The tough part for me is that the reason I use Reddit is for bullshitting with people about sports teams I like. Lets look at some of the communities here.
Baltimore Orioles -- There's one on lemmy.world with 150 subscribers. The last post is from 4 months ago and it's a game thread posted by a bot with 0 comments. There's also one on fanaticus.social with the last post from 7 months ago.
Carolina Panthers -- There's one on fanaticus.social with 3 subscribers.
Miami Heat -- There's one on lemmy.world with 10 subscribers.
Pittsburgh Penguins -- Again, lemmy.world with 11 subscribers.
I'd love to get off reddit but until there's actually people to talk with, this place is just never going to meet the needs of sports content that I use Reddit for. I had no interest in Bluesky until some people actually got on it as well. The Shutdown Fullcast for college football brought a bunch of people and fans there so it gave some utility to the site. Without utility, there's no reason to be here.
In the early years fo Reddit, those wouldn't exist either. You have to start with bigger groups (NFL, NHL, etc) and split them if they ever get big enough.
Discoverability is a serious issue on Lemmy. I'd wager there's a shitload of people here interested in the big US sports, but unless you know where the community is (and there's often multiple, and sometimes on instances you're not linked to), you're not going to see it.
There's just not enough users for any algorithm pushing of obscure communities you might be interested in either.
Yeah, people actively surrounding one water cooler aren't likely to go across the room to a different water cooler with no one there to start a new community. There's a lot of mental and social effort required there.
In the news in tech communities the moderation was becoming oppressive. If someone pisses all over the water cooler, then people are a lot more likely to change it up.
We see the same thing in the niche video gaming communities.