EW has a PhD but I can't seem to find any academic publications under his name. That doesn't outright mean he's wrong but it does mean that he actually has limited experience with the process. I have several and I've reviewed quite a few papers. I would say that peer review is a pretty good filter for garbage. Typically reviewers want to see shiny new ideas so if anything it over emphasizes innovation and discourages incremental improvements. As for gate keeping, I don't think so. Again, reviewers want to be WOW'd with new ideas.
In general, I prefer papers from peer reviewed venues over the arXiv. Good work does get put on the arXiv though so I can't ignore it completely.