I get your argument, but fundamentally

more freely available content would be great, right?

doesn't hold true. For example I don't need a flood of Instragram thots on my Mastodon or Lemmy pages, even if I got it for free. Quality is more important than quantity, I am here for in-depth discussions on current events and issues we face, with individuals capable of empathy and critical thinking. Considering the types of interactions that come from Facebook and related sites, I need better public reassurance that Meta's involvement won't tank the platform and it's vibe.

We've handled the Reddit migration about as well as we could have hoped, but the folks on Meta are a whole different beast. Many will be fine but there will also be a chunk of people completely blind to forum Nettiquite.

Lastly Meta acting behind closed doors is antithetical to FOSS development ethos. It leaves a bad taste in my mouth and I would refuse closed door discussions but be open to public ones. NDAs are rich corporations' tools to silence people.