It’s not really feasible to hold a vote on a decision like this when users can make endless socks. But it’s not really needed too.
Blacklist decisions are democratized in that the most popular instances can choose or not to participate in it. And if the users don’t like that the instance is a part of the block list they can create an account on another instance that doesn’t participate in it. If an alternate blacklist that doesn’t arbitrarily block instances based on the whims of the maintainers is created then the popular instances are going to switch to it if it becomes popular or users will go to an instance that does.
The fediverse is a free platform and users vote with where their activity is.