I'm not sure that even Lemmy has a monopoly on the fediverse anyways. But outside of the fediverse, breaking up the tech monopolies and enforcing net neutrality are steps in the right direction.

For the fediverse specifically, I'm not sure. One thing that might help is to make user accounts and magazines (communities) more portable. So if one signs up on the wrong instance, it's easier to move to a friendlier instance. Currently, some folks seem to set up their own instance specifically for a community that they have planned explicitly to avoid this problem (but that makes it even harder to get a new owner if the mod-admin abandons the instance).

Of course, the technical bar to setting up and running your own instance is a bit higher than just signing up to, for example, fedia.io (And that's just if you want to run vanilla - you generally have to be an actual software dev if you want to customize the software that your instance runs.)

But coding software, and moderating a community, or an entire instance, are all different things and I suspect that there's not much overlap with the first one and the other two. So I don't have any good solutions either, just suggesting that if the fediverse required everyone to set up their own instance to join, we'd likely be in a pre-Eternal September phase.