Without the publishers filtering you can't just pick a book at random and be ensured it probably won't make you want to claw your eyes out (at least publishers would clean up the major spelling mistakes, grammatical errors, and incoherent plots).
So what is left is popularity, and as already established that doesn't stop shitty authors writing books.
Peer recommendations are a real crap-shoot unless you have vetted your peers thoroughly, which takes time.
Whoever can build out an automated system to rank and recommend self-published books will make a fortune.