Im joining in on the reddit ditching thing, and was kinda worried at first that i wouldnt be able to like use it the way i did reddit as it feels like a whole new place, but after engaging with posts and people and actually being a part of lemmy rather than being lurk mode all the time i was pleasantly surprised with how easy it is to become a member of the community, theres a reasonable amount of subs (or whatever the other word for em is) that fit my interests, enough linux content and shitposting for my liking, and the overall random posts made by people equally fed up with Leddit. (also i admit i used reddit a little cus there was this post on the fedora sub showing how to fix a sound issue i been having after a recent update)
To be fair, Reddit doesn’t merge similar communities either. You could have /r/cats, /r/catpics, /r/cat_pics, /r/PicturesOfCats, and so on. The point is, Reddit also needed time to establish popular communities before they took hold. I think it’s less a structural issue with Lemmy and more just a small forum problem. In time it should self correct so that when you look up “cats” on Lemmy, the overwhelmingly most popular community pops up and you can subscribe to it. The one downside is that you could have multiple /c/cats communities on different instances, but that still won’t be that big of a problem. The most popular one will still be the first search result and it won’t be too hard to remember that it’s the Beehaw cats community that’s the popular one (not literally - just to use a random example instance).