As far as I can tell from my venture into Mastodon’s feeds, the demographics of that part of Fediverse isn’t that different from what Lemmy has: the same political takes, FOSS stuff, “big corpos bad”, etc.
I wonder, is there anything that Mastodon excels at that Lemmy just doesn’t provide? For example, I noticed that there are game developers and artists posting their stuff on Mastodon. Not many game developers (or any creatives, really) on Lemmy though.
Mastodon is personality focused rather than topic focused like Lemmy/piefed/et al.
If there is a person or organization that you’re interested in following (or if you’re a person or organization that is or aspires to be followed) then mastodon is the service for you.
People-oriented networking feels like staring in the void when one is asocial enough. In topic-oriented networking one does not need to contribute that much. Maybe that’s why Lemmy seems better than Mastodon for me.