You either have gatekeepers--publishers, agents--who bring some level of quality control or you throw all that out the window in service of democratizing access. Not that they would, but Amazon could absolutely only accept books from legit publishers but can you imagine the howls of protest here were they to do so?
I'm not at all sure you're wrong. Or at least there may increasingly need to be some reputational authority whether it's as a person's real-life identity or authoritative third parties. You sure can't trust reviews or self-written puffery.
If one is cynical enough, it's easy to imagine shifting back to a world where you have a relatively small number of (more-or-less) trusted media outlets you have to subscribe to, some big publishers, and everything else is sort of hit-and-miss and most people won't bother with.
