I’m not sure why you’re giving a history lesson when I already acknowledged that point in the comment you are replying to.
It's because, despite claiming to have acknowledged the problem, you're still making such an incredible false equivalency - comparing joining a new Lemmy instance to moving out of an authoritarian country - that you either completely misunderstand what you're talking about, or you're arguing in bad faith.
Sure, I theoretically could create my own instance, but then I would have the same problem as current instance admins, even those who are sympathetic to these ideas, as I suspect Lemmy.world and my own are. That there is no structure within Lemmy to enable collective decisions to be made or executed, and I would need to build them from scratch.
You'd have full control over your instance, and could, if you built up a community, use any online voting method you wanted - of which there are plenty - to poll your userbase and gather their opinions.
However, ultimately, you'd be the one paying for the instance, and doing the work to set it up and keep it updated and running. What would you do if you attracted a userbase that had views that were completely counter to your own? What if you attracted the alt-right crowd, and what got voted into place was all hate-speech, nazi rhetoric, and intolerance? (I assume you disagree with these things...) Would you continue paying for and hosting the instance, just because that's what was democratically decided, even though it's no longer an instance that you want to participate in? Could anyone really fault you for not wanting to do that?
A better method might be for you to make clear your own opinions - either via a post explaining them, or via a pre-defined federation / defederation plan - and let people join your instance who agreed with those decisions. Which, incidentally, is how most instances currently operate.
Be the change you want to see in the world. You don't have to code in an integrated solution; all you'd have to do is set up an online poll, listing all of the other instances up for consideration (such a list can be pretty easily obtained - for example from https://lemmy.fediverse.observer/list ), run a new poll on regular intervals, say, every 2 months, and let anyone who is interested vote. Then, you update the defederation list based on the results of the poll.
However, I think you'll quickly run into the other problems I outlined which, unfortunately, can't really be changed. You could require everyone who's participating in the voting to also be contributing time or money to run the server, except that then you're operating a plutocracy, not a democracy, so most likely, you'll need to be giving up your time and money to make your desired server administration a reality.