Lemmy (or at least lemmy.world) was bonkers levels of buggy last summer during the reddit blackout. Like, literally unusable levels of buggy. Getting the word out that it's (mostly) bug-free now would probably be good, because I'm sure there were many redditors who tried it and quickly swore it off as a pile of shit.

Otherwise I'm in agreement that the instance-selection part of sign-up is a huge barrier, because what instance you choose is actually really important but it's overwhelming when you're just getting started. Plus not being able to migrate your account/communities/posts to another instance if yours goes to shit/shuts down/turns out to not fit your needs makes the fediverse feel really unstable.