So, the vetting process is actually extremely valuable. Refereeing papers is a super important service. It's just not one that these journals meaningfully provide. They either don't pay the peer reviewers, or they pay them something completely nominal. They do it because they want to, and for prestige. That is the only hard part of operating a scientific journal. The rest is just hosting and distributing static content. If you have a team of peer reviewers ready to go, you could literally setup your own scientific journal on WordPress for free, right now.