Hmm, I'm not sure what the end goal is. More devs would be the ideal I suppose. More people who can respond to questions is good too (I posted a while ago, asking why Lemmy sent an Undo of a Dislike as an Undo of a Like, and people gave their opinions, but it ended up being me who eventually answered the question).
I can't imagine myself ever submitting a PR - aside from my rubbish programming abilities, the GitHub politics of many open-source projects is often the biggest hurdle (taking ages to craft a PR right, for it to be dismissed by a lead dev with an airy "I'm not sure we need this ..." or "Oh, I've solved that problem - and so much more - on my private branch ... [that'll never see the light of day]").
Also, whilst I've seen the suggestion that the front-end is being re-done in Rust, for now it's in NodeJS, and for me it's the UI that needs the most work (erroring, rather than waiting for unknown remote Communities to resolve, stops so many of them from ever taking off). Other UIs are available of course (who handle stuff like this better) but the implosion of Tesseract suggests that anything that isn't the official one will ever get any back-end support - see https://lemmy.world/post/9014308 for evidence of some GitHub drama. Same is true of mobile apps too - Jerboa is arguably the worst, but it's the only one that'll ever be official - and that's a whole different bunch of technologies.
Sorry for such a long reply. I just meant that even if a bunch of us learn Rust from this Community, it won't necessarily lead to a better Lemmy, 'cos knowing Rust is only a small piece of the puzzle.