For me it's been like a splash of cold water to the face, remembering just how fucked up 
tier liberal takes were, are, and will likely continue to be.
I'm sure there's downsides to complacency, but it was nice having some ground assumptions when going into a thread, like "society can and should be improved somewhat" or "the ruling class acts in its own immediate self interests and any other claims regarding their motivations are propagandized lies" or "climate change is real, it's bad, and it's getting worse," or more trivial stuff like "Tesla cars aren't good."
I'm sure potential comrades are out there and while it really is necessary to reach out to more people at some point (offline too, orgs especially, but while we're here, you know?), it's been sobering to realize just how far rightward mainstream "progressive" liberal thought really is on average. 
My experience began in earnest when I launched Matapacos, though I had dabbled earlier. Overall, it has been pretty positive. At first, I was worried about catching the ire of the mega-instances, but as time went on, I found that the vast majority of cool people that I end up following aren't domiciled there anyway. The same will turn out for Lemmy in the long run, but the Lemmy network is nowhere near as mature (politically) as the Fediverse itself. Things will be volatile for a bit. The whole federation / defederation war will burn out at some point, and communities will develop on either side of the wall.
footnote
By mature (politically) I don't mean that it has universally good politics, but that it is less volatile and that many people have transcended the initial stage of "go to the big instance" to finding an instance which aligns with their trade / craft / politics / interests.We just pulled the plug on mastodon.world (175,141 accounts) and it only severed 56 follows (total, for all users on the instance, incoming + outgoing). Averaged out, 1 out of 3 users lost ONE person from their follow list.