I think what you're looking for is the next step of plan S:
https://www.nature.com/articles/d41586-023-03342-6But in the meantime:
The first step for acceptance is the journal editor - in lower tier journals, that's an unpaid Professor, in higher tiers it's a paid staff member (usually academic background too) - who decides whether the journal thinks this paper is a good fit or not. Most papers die there, too low impact, too niche outcomes, not enough wide readership etc.
If it has passed the editor it goes to peer reviewers, unpaid academics, who make similar decisions; is it technically sound? Is it impactful?
Impact is measured by the number of citations this paper will have, a bit of an educated guess. A paper on an obscure seagrasses will have few citations, a paper on a novel cancer-defeating mechanism will have many.
High impact factor journals are selective in which papers they accept (via editors and journals) to keep up the high impact factor. That double-gated decision is what turned into a stamp of approval; it's the journal's brand which is the lynchpin for the academics' career, not the peer review