Dating in 2023 sucks. Why isn't AI helping?

I believe the main issue is the bad matchmaking process.

I don't think that's likely.  Compared to previous generations, modern matchmaking is orders of magnitude larger and more detailed than it was.  

The main issue (IMO, as an outside view, having been married and glad of it for many years) is broken expectations of participants.  Most young people seem to feel that they need to find the perfect partner out of millions, who's a great fit for them and will somehow know it.  Most DON'T seem to want to get to know a few dozen (at most) potential mates well enough to figure out how to change to match better, and how compatible they are in terms of communication and compromise.  

As to your direct question, this kind of questionnaire-based matching has been around forever.  AI doesn't really change the basics, though chatbot-elicitation of personality traits may have promise.  The problem is that people lie to themselves and others, and it gets Goodharted almost immediately, so loses much of it's objectivity.

Although the dating web sites, I'm sure, have accumulated a lot of data about people looking for dates, I doubt any of them have taken the trouble to collect accurate information on how well the dates turned out especially when the criterion for success is whether the date leads to a long-term relationship.

So (at least if you want to help those looking for long-term relationships) you can't just buy the data you'd need to train the AI from an existing dating site: you'd need to collect it yourself and ensure it is accurate, which is expensive.

Contrast that situation to the situation of training an AI to play chess: it is easy to program a computer to determine with 100% accuracy which opponent won a chess game, which keeps down the cost of training.

The problem is coordination. Suppose that the AI gave you the perfect matching algorithm. But still, you have no users to apply this algorithm to, so you can't prove that it works.

The existing dating websites do not have a reason to change -- their current websites generate profit. You need to make your own website.

Okay, so now you have a website with a potentially perfect algorithm, but zero users. You start advertising. The first few users come, but get a poor match, because there is little to choose from. So they leave.

Someone like Facebook would be in a better position to do this, because they already have tons of users, and can advertise to all of them at the same time for free. So they could add it as an extra functionality to Facebook, and feed the algorithm the data about the users they already have. You would just have to consent to receiving dating suggestions. Also, Facebook would have less of a problem with fake profiles. (There are many, but not as many - as a fraction of total accounts - as there would be on a dating websites. Also, most fake accounts on Facebook are for marketing or politics, so they wouldn't be interested in dating.)

Not sure about the incentives, though. Maybe people who are happily in love, spend less time scrolling Facebook endlessly? Then Facebook would kill the goose that lays them golden eggs.