Strange, I had used it for some weeks, writing also a couple of posts there (and then lost interest), and never had any problems regarding performance. This was in 2016 or 2017 though, maybe they scaled down the infrastructure, at least on the steemit.com server.

There could be several server operators competing here. They could add their own advertisements for example, or finance the server and domain via the mining/minting process. It's likely that one server would become the most popular one (due to duplicate content issues on Google, for example) but as long as other possibilities exist, the risks related to centralization are minimal, because if the operator misbehaves there's another option around the corner.

And for those who want to access directly the content on the chain without wanting to access via a "centralized" domain, there is no technical hurdle to simply write a client where also a content browser / posting interface is included.

But I sorta agree - this is something for the far future, considering not even Epochtalk is ready after 10 years or so ... But I personally think positively about that option

Regarding the backup copies that already exist (TryNinja etc.), I think the problem is that while these copies are stored only by a few people, there's still a relatively high risk they get lost, or corrupted, or whatever. So in general the OP's idea is not bad, I think.

If this ever comes near reality, I would strongly oppose to store the images on-chain or in the main torrent. That could attract the wrong people. Images can still be included via external servers like talkimg, or via external image torrents.