Please specify why one's self- or projected-image as a rationalist has significant impact on this decision.  IMO, the question of whether to propose is far more interesting than the how.  And that also requires much more input that whether one or both (or multiple) partners consider themselves "rationalist".

Or you could just take the standard rationalist answer: "yes, if that maximizes expected utility".

There is a big difference between the title and the post text: the word "you" vs "a."

For me, personally: yes, I think it was the right choice. For a generic unspecified "rationalist" - it depends on both them and their partner. There's nothing fundamentally wrong about valuing traditions and symbols that feel meaningful to you or your partner. In my case I found ways to layer multiple sources of meaning/symbolism without spending a lot (which is good, and something we both appreciate, for its own sake and because for various reasons the ring doesn't get worn much). That said, if it ever got stolen or destroyed or something, I don't think we'd replace it.