Many subreddits have outright collapsed and will almost certainly never return.
But the subreddits that stayed seem to hit the frontpage and attract new followers... All the Redditors looking for new hangout spots. Post quality has declined as a result, but the subs who stayed have seemingly absorbed the traffic.
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Lemmy.world usage spiked dramatically, as has Mastodon.world. I think these alternative open source communities show lots of promise, though many decisions at Lemmy seem naiive right now.
The adults seem aware of the Lemmy problems however so I remain hopeful. If your community is text based, Lemmy is likely a good fit.
Picture based communities have a NSFW / trolling problem that is still an open question. If trolls can post CSAM to threaten the moderators / admins, what are Lemmy admins supposed to do about that?
DeFederation (and temporary DeFederation) are okay tools for this problem... But better tools need to be built into Lemmy. Random server #244 doesn't necessarily deserve to be defederated if just 20 or so trolls are posting CSAM and threatening Admins. Nominally, a tool that more selectively bans users (or new users only) instead of cutting off the whole server would be ideal.