The reddit concept of subreddits also doesn’t work well with federation IMO (at least no Lemmy’s implementation).
Want to talk about video games? Well, there’s no /r/games, instead there are bunch of different /c/games on different servers with varying amounts of activity. You basically gotta make the “pick a server” decision again whenever you post something. If you make the wrong choice, your post might not get seen by anyone, and even if you post to the biggest sub, you’ll be missing out on eyeballs from people on other servers who aren’t subscribed to that instance for whatever reason.
For example, lemmy.ml/c/linux_gaming and lemmy.world/c/linux_gaming have around the same number of subscribers. Should I post to both? Maybe the same people subscribe to both, so that’s pointless? Or maybe I’ll miss out on a lot of discussion if I post only to one? There’s no way for me to know.
For me, it makes Lemmy less useful than reddit for asking really niche questions and getting useful answers. For posting comments on whatever pops up in my feed though, it works great.
I don’t have any good solutions to this, and I’m sure it has been considered already. When I first joined, I remembered seeing people bring this same issue up, but it doesn’t seem like it went anywhere? (Or maybe it did?)
For that side of reddit, you’re right.
But for the uniquely useful side of reddit, federation won’t help. If I post a question like “how do I get this obscure game to run well on this obscure Linux distro?”, nobody is going to repost that for me, and if I don’t maximize the amount of eyeballs on it, it’s unlikely I’ll get an answer. My best choice is to post it on reddit, either in /r/linux_gaming or in the specific game’s subreddit.
I assume that most users who post anything at all on reddit do it to ask questions like that.