A growing number of instances (mainly of Mastodon so far) are signing an ‘Anti-Meta Fedi Pact’, pledging to block any instance owned by Meta in the fediverse.
I don’t know how big this will get or how effective it will be, but if you run a fediverse instance, you should take a look at this https://fedipact.online/
A good actual reason is to preemptively kill any attempt at embrace, extend, extinguish. Meta is like a cancer. It won’t stop until it has taken all of our users and the fediverse collapses. It’s less gatekeeping and more keeping poison out of the system.