I’m no ActivityPub expert, but what people more knowledgeable than me have pointed out is that this results in fragmenting the Fediverse, which ends up hurting it on the long run. I’d definitely not want to be on an instance that federates with Facebook, but I also wish none of the larger ones choose to do so.
Both Twitter and Reddit have failed to become profitable. And Twitter’s in a far worse position right now than Reddit, because of its massive debt and lack of employees to fix or moderate issues. And since Reddit, who never had to pay for moderation, could not become profitable, it had to make some drastic changes toward that goal. Even if that dissatisfies users.
I was on Reddit for almost 10 years when I deleted my account. And while the platform will survive, it’s difficult to say the same about Twitter. Not only was it a far worse experience to be on the platform after Musk acquired it, but now it’s almost impossible to use it. People paying for the subscription have fewer issues, but I doubt that’s going to drive up subscriptions, as Musk most probably expects.