I'll play devil's advocate here -- I hate Meta, but Meta apps supporting activitypub would be a huge benefit for adding users to the platform.

Like other small social platforms, the fediverse has a fundamental choice to make between quantity and quality. The quality of Reddit took a nosedive in the last 5-6 years as the platform grew. I'm not saying it was always great in "the old days", but recently all of the big subs were just page after page of the same memes, stupid arguments ("it's called soccer! It's called football!") that have been had a million times, and the same jokes.

So the question is -- how much does the fediverse want to grow? The thing keeping me from deleting my Reddit account right now is some of the sports communities there, and things like a local urbanism group from my hometown.

Having Meta apps support activitypub could help establish that kind of userbase. At the same time, the influx of users could drastically reduce the quality of the platform. It's a balance that has to be struck by the community.

The cool thing about the fediverse compared to other platforms is that the structure allows this kind of thing to be decided fairly democratically -- each instance can "vote" by deciding whether to federate or not, and if we all agree we don't want them, everyone can defederate. If we're 50/50 they'll federate with half of the community.