If a free service requires fairly involved explanation of how it works, its not going to catch on. So the problems you are asking about don't need solving because the nature of a de-centralized social network prohibits widespread adoption. Previous flavors of decentralized internet forums never gained widespread usage either and the people that administered them typically didn't want them to.
Likely decentralized networks might end up like web3 or torrents.
You're also likely to get partially centralized communities again like 4chan or the more extreme 8chan, or something fairly sustainable like Something Awful.
Bluesky has a more interesting compositional design (ATProto), seeing more ex-X users there every day
Both can be monitored by creating a similar UX for users, running large data nodes so most dont notice the difference, and then injecting ads in their interface or charging a monthly fee
Both open the door to increased competition, because switching cost should be lower (in theory), which is what we really need.
I definitely think decentralized architecture is the better way to build social media.
It's hard to beat "friends chat" for decentralization. And it's hard to beat Facebook for centralization.
Good luck.
It happens more because their skills are more aligned with adding and supporting new racks at the data center, or advertisors/corps are frantically searching to create more artificial digital Real Estate on top of which to put up digital billboards and capture attention.
So you have to be clear about what problem you are trying to solve and for whom.
Also check out the UN report on the Attention Economy. It provides lot of analysis of the space and food for thought on how future social should be designed.
For example, you might reply to a post on one instance, but everyone ends up missing your reply. Was your reply just not worth reading? Or was it a problem with federation? Both can happen. If there's only one giant instance the behavior is clear and ordering makes sense, but with lots of smaller instances you can have ordering issues, propagation delays, and the like.