Fediverse can't sustain many niche communities with its level of activity. Even gaming communities on lemmy don't have enough traffic to constitute communities for individual games. I can't do after-episode TV discussions on Lemmy because there wouldn't be enough people commenting to warrant it. If I wanted to search for a D&D game in my local community (a huge US city), I couldn't do it via Lemmy.

I can do all this on reddit, which I intend for Lemmy to replace, but I can't do that yet. So I still crawl reddit for the needs Lemmy can't replace, but I'd rather never have to open reddit in the first place.

Same is true for every alternative platform on Fediverse. I'm still using all the mainstream apps I intend to replace.