This is an interesting take from @kissane. I believe more nuance is needed.
What people on Mastodon are seeing is everyone leaving to go hop on the new shiny thing.
Enthusiasm for ActivityPub is being sucked out of the room in favour of something that hasn’t left beta and hasn’t proven to scale for federation.
And knowing what we know about Dorsey, VC funds, and hype cycles, people perceive this an existential threat to the Fediverse.