Lemmy has already massively improved since I first encountered it a few years ago. There are so many more users and so much more activity. I expect the usability issues will be worked on and resolved in time. Without a corporation behind it or some way to meaningfully monetise it, process will be slow of course, and I'm not sure it could ever become mainstream in the same way that Reddit has.

In terms of discovery, there is a centralised community browser of sorts... but you'll see it's got quite a way to go: https://browse.feddit.de

However, as someone willing to put the time in to learn something new I've found my efforts rewarded. It does take longer than 10 seconds to get used to Lemmy and the fediverse, but I'd say no longer than 15-20 minutes really. I enjoy being part of something new and I hope it lasts. Perhaps it won't hang on to many of the new users it has gained, but I expect this won't be the last time Reddit does something its users don't like and next time around more will stick, hopefully presenting a very good alternative.