The people who would use a Meta variant will use it, and people like us will not. This reminds me of the interview with the Mexican restaurant that spawned Taco Bell. The lady who owned it essentially said, "I'm glad he (the founder of Taco Bell) was able to take our teachings and turn it into something. Good for him." If they build proprietary code, that's nice. ActivityPub will still be the same open-source code it's always been, and all of the Fediverse stuff will still exist. It kinda sucks that Meta is trying to make it seem like they're the good guys, but in the end there isn't much they can do to the already established stuff beyond make their own.

Edit: also, if they do try anything, we at least have previous data and most of the people who care about freedom to privacy here that I'm sure we could come up with something. We're not getting blindsided like with Google and XMPP back in the day.