On top of that, you'll also have to make sure that your instance admins defed with Meta

I think most people currently on lemmy would agree, but most people aren't on lemmy. Like it or not, if Meta started a fediverse instance tomorrow, 90% of the fediverse would end up going through it. They would just make it so easy that most people wouldn't even know they were in the fediverse (which I still believe is a better world than how it currently is).

Then your choice isn't just "do I join a meta instance", but also "do I interact with users/communities" on a meta-owned instance? The upside will obviously be the amount of content (ex. populated niche communities) available. The downside is that Meta will mine anything and everything they can from you. I do think lemmy is architected in such a way that they won't have lurking data because your local instance "clones" threads for lurking by local users, so maybe it's not that big of a deal. DMs would still not be encrypted though, and meta certainly won't endorse communication over matrix.