The problem really is that lemmy doesn’t have the critical mass of users to support many small communities that are all self sustaining. And discoverability is so bad for communities it’s entirely likely that if there are 8 people out there that want to discuss X in the fediverse, 3 are in one community, 2 in another, and 3 in a third, and none of them ever finds the others. The lack of users causes a lack of content and they all the up not engaging at all.
If you have enough users the idea of multiple communities holds water a little better. But I think it’s a significant barrier to actually gaining those users.
Multi comms are a good idea, agreed.
As for weak discoverability encouraging tendency to gather on larger comms…I agree, but I would just add that it does require motivated and proactive users. This isn’t a given. In my hypothetical, those people started their own communities about something they like, and had a few users but not many. Do they at some point decide to give up and search for another community? Or do they just forget about it because there’s never any activity and they don’t go there? How many searches should they do without finding anything?
As a real life example of my own, I’m a Green Bay Packers fan. I wanted to find a place to take part in active discussions about the team. I joined what seemed to be the biggest community and posted a few things, commented in threads. Most would get one or maybe two replies. Often nothing. A month or two later I searched again and found a few more communities that had popped up. All around the same size and activity level. Joined them, also crickets. The members there didn’t congregate around a larger instance, they created more small instances and then all of them ended up largely abandoned.
I don’t know exactly why that is, but I’ve had this experience with other topics too. Maybe instance tagging with a recommendation algorithm that suggests similar communities in the fediverse based on the community you’re in?