Conferences and journals are a filter. If your paper can't pass a few rounds of anonymized review (for a conference) then it probably isn't worth the readers time.
As an example, arXiv is has a lot of great papers but it also has a lot of bad ones. I'm unlikely to go there to find a paper unless someone referred me to a specific one.
I've never had a paper rejected from a conference, and I've seen some pretty shitty ones at conferences. I think this statement is pretty field-specific.
That said, in the CS and EE fields at least, the use of 10-12 referees for a short, dense conference paper is a really good idea. It would appear that this works primarily because of... drum roll ...the social norms and incentives in place within these specific fields.
One would think that this wouldn't happen simply because it is (I think) a combination of two of the most well-known logical fallacies, "argumentum ad populum" and "appeal to authority" https://yourlogicalfallacyis.com/appeal-to-authority
I am extremely dismayed by the fact that, in a career where (of ALL careers!) the evidence should ostensibly speak for itself, papers (and their information) are essentially pre-rejected or pre-accepted based on reputation