I would not really hold up s3 style object storage as particularly useable. Discoverability is arse, name collisions are easy, listing contents is extremely inefficient, updating access control is a fucking nightmare.

I don’t think the demands of distributed computing should necessarily inform design decisions for single user or mainframe computing, I agree that performance is unpredictable but that’s why you don’t rely on hammering the disk for performance. The underlying hardware is always going to be a bit unpredictable anyway, if you want stuff like always having atomic transactions you are going to be doing a lot of copying, that wears out hardware and is just unnecessary for a lot of applications.

I’m not saying they’re always good, just that saying they’re (always) a bad abstraction is wrong.