Yeah, I’m a little confused by the doom-and-gloom regarding all this. Meta/etc. can only ruin the Fediverse if we let them. I really doubt most people currently on lemmy/kbin/mastodon are going to abandon the smaller instances in favor of a Big Corp instance, which IMHO is the big way they can ruin it (consolidate users from smaller instances and then pull the plug). I think there is even an opportunity here to really grow the Fediverse — smaller instances can (and should!) steal users from Big Corp instances.
Of course this may just be wishful thinking. With their track record, who knows what’s possible I guess. (For example, I fully expect non-meta users to be 2nd class citizens on a meta instance…)