Yeah but in this particular case it really needs to happen at the instance level rather then the user level, and preferably all instances at that. It's about mitigating the damage that Meta/Facebook are going to do (to the entire fediverse as a system) more than it is about not seeing shitty low-effort racism or whatever they'll have there.
If I could actually trust Meta to be benign then I'd maybe agree with you about just blocking their shit as a user, but there's just no chance of believing that about them.