Yeah discovery is kinda terrible. Luckily there's tools like https://lemmyverse.net/communities and https://lemmyverse.net/kbin/magazines, but something like that definitely needs to be built into Lemmy itself.

To get the community started you can put it on !newcommunities@lemmy.world, sub.rehab if there's a counterpart on reddit, and maybe advertise it in any relevant places. After you get just one subscriber from an instance everyone there will be able to see it in search and the all tab.

This whole visibility thing is a serious problem

Yes. I have been preaching that since I first started using lemmy in June. Every time I bring it up my comment is downvoted to oblivion. The way it currently works is borderline abusive to new users of lemmy.