If people have to follow breadcrumbs to find which of the dozen groups is active, if any, very few people are going to join.

On reddit, if you wanted to find a sub for airbrushing, you would type in /r/airbrush. That was it.

On Lemmy, there's no central location for communities, but even worse is that most of the big instances WILL have a community with that name - it'll just be a dead community that someone started but never took off, so there's a bunch of false leads.