There are several examples of communities moving from instance to another, or refusing a mod powertrip.
!unixporn was an attempt from the mods subreddit to get the community back, but most of the people rejected that and stayed on !unixporn.
Small scale example, but I like the show "the Office". !dundermifflin is the historical community, but as some people are not fans of lemmy.ml, we moved to !dundermifflin, which is now the most active community on this topic.
I guess that shows that community takeover is possible, and does not need additional tools, just some time and dedication.
Also, keep in mind that except if there is a real reason (admin/mods powertripping, problematic instance direction), there is no incentive for users to move to another community. But the important thing is that the possibility is very much there, and helps keeping everyone in check.