You are allowed to edit Wikipedia

You are not allowed to refer to primary sources such as journal articles but must only refer to secondary sources such as textbooks or newspapers

This is not true. I could drone on about the Official Policy but maybe the better rule-of-thumb is:

(1) Don't edit articles to push one side of an existing hot-button political issue, it's hopeless unless you have a ton of wikipedia experience and a ton of free time,

(2) If you write things that are correct and widely-accepted, they're pretty unlikely to be deleted, regardless of what source you cite, or even if you cite no source at all. If other people don't like the sourcing but do like the text you wrote, they're more likely to improve the sourcing than to delete the text.

(3) ChristianKI's advice was actually posting on the talk page rather than editing the article directly, which is always a good bet. And if the article is so neglected that nobody does anything about your talk-page comment, then that's a good sign that you can probably just go and edit the article without anyone bothering you.

One small example: You are (or were when I looked) required to refer to male genital mutilation as "circumcision" and are not allowed to refer to it as "male genital mutilation". The female version may not be referred to as "circumcision" and must be called "female genital mutilation". 

I'm not sure what you were expecting. There are a gazillion people who think "circumcision" is the obviously correct term, and a gazillion other people who think "genital mutilation" is the obviously correct term. Of course there's going to be an Official Policy on this, settled long long ago, otherwise people would spend all day in endless "edit wars" where one person changes it, and the other changes it back, and the first one changes it back again, around and around forever. You're welcome to think that the Official Policy is wrong, but I don't think it's reasonable to expect that you can just easily "fix this problem" the way you can easily fix other problems on wikipedia pages.

wikipedia's view that there is a definitive version of the truth on any given issue makes it utterly hopeless at covering anything that is controversial.

I don't think that's fair, I think there are lots of articles that present both sides of a controversy pretty well, for example minimum wage seems pretty good.

In fields where there is no political controversy things are not so bad. But you are still subject to the deletionistas who will find any possible reason to nuke your hard work. 

I don't want to say this never happens. I think you need a sufficiently "thick skin" that if 10% of your edits are deleted for stupid reasons, you're generally happy about the other 90%, not stewing over the 10%. 

Wikipedia’s articles on circumcision and FGM include coverage of the ethical controversy both around the practice (in the case of male circumcision) and the colonialism inherent in the name (in the case of FGM).

Their page on source selection states:

“ Many Wikipedia articles rely on scholarly material. When available, academic and peer-reviewed publications, scholarly monographs, and textbooks are usually the most reliable sources. However, some scholarly material may be outdated, in competition with alternative theories, or controversial within the relevant field. Try to cite current scholarly consensus when available, recognizing that this is often absent. Reliable non-academic sources may also be used in articles about scholarly issues, particularly material from high-quality mainstream publications. Deciding which sources are appropriate depends on context.”

If you are alone you need to understand the rules reasonably well. 

What I propose here is just to raise issues on talk pages and if someone else already wrote something make a new argument. Often this doesn't take long. 

You are not allowed to refer to primary sources such as journal articles but must only refer to secondary sources such as textbooks or newspapers, which are often out of date, biased or wrong.

Rules in Wikipedia are a matter of consensus. If you care about the rules it's easy to give your opinion when rule changes get proposed. 

https://en.wikipedia.org/wiki/Wikipedia:Feedback_request_service is a way to register yourself to get regularly a message on your talk page for one rules discussion. While a user that only participates in rule discussion and nothing else is likely seen as a bit dubious, if you write short messages on the talk page whenever you think something should be improved, 

One small example: You are (or were when I looked) required to refer to male genital mutilation as "circumcision" and are not allowed to refer to it as "male genital mutilation". 

Wikipedia's rule is to use the terms that are most commonly used by authoritative sources out in the world. Given how language is used out in the world it's often not consistent. 

It doesn't matter whether it's a hot button political issue or an unpolitical one's like deciding whether to use the greek or latin name for an anatomical structure where things would get easier when latin names get used consistently. 

The opinions of the doctors who make money from this operation on males must be deferred to as definitive. 

That's not true. If you could for example argue that authoritatie sources like the New York Times and the Washington Post use another term then the doctors you have a case within the rules of Wikipedia.

While you can argue that rules should be different (and you actually can argue that in RFC's in Wikipedia) it's deferring to authoritative sources is a rule that works for finding consensus.

And wikipedia's view that there is a definitive version of the truth on any given issue makes it utterly hopeless at covering anything that is controversial. 

I think this misunderstands Wikipedia. Wikipedia's goal isn't truth but to reflect the current consensus among good sources. This is argued quite explicitely. 

I do think that a place where I can go when I want to read the consensus among good sources about a topic is valuable.

This seems a little harsh. Sure Wikipedia has many rules, mostly to prevent bias or people pushing agendas. It’s not perfect, but in general I have found it to be a reliable, neutral source of information especially in controversial subjects such as Middle East politics for example.

Also research shows that Wikipedia is a reliable source https://www.zmescience.com/science/study-wikipedia-25092014/ although I’m sure you can find research that shows the opposite.

And as the original poster says, if you find something inaccurate, spend 5 minutes to give back and fix it. I have made hundreds of small edits and maybe only a handful have been deleted / rolled back

I can’t talk about your specific examples of course but I would trust (cited) articles on Wikipedia above most sources on the web.

During my stint volunteering with the FLI, I worked on a project  to improve Wikipedia's coverage of existential risk. 

An organization having a project to change Wikipedia is not what Wikipedia is about and triggers immune system response of Wikipedia. 

The way to engage with Wikipedia is to start by doing a bit when you naturally come across a Wikipedia article with issues. 

For the whole EA endevear that incountered resistence, it's worth noting that Jytdog who was one of the main admins against it is now banned.

That said I do agree that creating new articles in Wikipedia can be hard and I would prefer policies to be different and while that is good it's not the core of what I'm advocating here. 

In cases where an edit is very likely to be reverted when done on the article, the place to have the discussion about the content in question is the talk page. That's why I spoke in my post about voicing issues on the talk page. 

The powers that be should really change this.

Wikipedia is democratic there are no "power that be". Someone has to write the RfC and then enough people (there's a minimum number of edits to be eligible) need to support the RfC. Admins don't have any special voting rights.

If the people who are annoyed by the status quo leave instead of voting in the decisions to have better policy, policy won't improve.

That's great to hear. Effects like this are what I was hoping for.

This is true for the actual page but not for the talk page. The talk page is where the disagreement about those pages get resolves and where it makes sense to speak up to push consensus in the right direction.

If there are already multiple missing links to that page it will be easy. If not less so. Knowing this, when I tried to add a page about an artist (my late father-in-law) I first created that context - the institutions he worked at. 

While missing links can be helpful, it's not central. When thinking about creating a page about a person it makes sense to first read the section in notability:people that applies.

In the case of artists its:

Authors, editors, journalists, filmmakers, photographers, artists, architects, and other creative professionals:

1. The person is regarded as an important figure or is widely cited by peers or successors.
2. The person is known for originating a significant new concept, theory, or technique.
3. The person has created or played a major role in co-creating a significant or well-known work or collective body of work. In addition, such work must have been the primary subject of an independent and notable work (for example, a book, film, or television series, but usually not a single episode of a television series) or of multiple independent periodical articles or reviews.
4. The person's work (or works) has: (a) become a significant monument, (b) been a substantial part of a significant exhibition, (c) won significant critical attention, or (d) been represented within the permanent collections of several notable galleries or museums.

So when creating an article about an artist you have to search for sources that demonstrate either of those points.

This is a bit like saying: "The politician that win the election these days are crazy so I stopped voting". The fact that a lot of bad calls get made makes it more important to engage and not less.

(I think donations are a different matter, and don't think that there's a strong case for donating)

The claim I'm making in this post is that it takes multiple people to change consensus on a controversial Wikipedia page. 

Gwern experiments suggest that one person alone won't do it and thus I don't see it as a contraction to my claims.

That’s not my experience. These days I find innocuous edits to innocuous articles are very often reverted by someone who has appointed themselves the authority on the article in question. Only edits they really like will stay.