Personally I think that if there was like a central link/front end to access everything and then have each user be able to have a recommended list of instances/hosts to access would be a more user friendly solution and a better solution for search engines. I know the fediverse is about decentralization but having a central front end and decentralized back end seems easier for new users. And then for the back ended hosting aspect each host would be able to manually pick which instances or communities to host and mirror. I'd like to hear your ideas since I have no idea what I'm talking about.
Yes, but someone ultimately pays for the instance that is centralized. It's that owner that could be susceptible to turning evil at worst, and misguided at best.
This is not infallible either. If money or power comes into it, you can bet on corruption.