It's not the same as a github PR because wading through a mountain of badly written papers is work researchers do not want to do. That's what a publisher (like Elsevier) does. See example of Elsevier employee Angelica Kerr.[1] It should be easy to see that scientists would think it's a waste of their time to do Angelica Kerr's work.
I didn't get a chance to respond to the reply by allenz that suggested that journal chiefs should hire their own editing and administration staff. Again, that "solution" makes the same mistake of thinking scientists will do something they have no interest in doing. They don't want the hassles of "contracting" an editing team.
The research publishing is not a "software problem" that's solvable by a "software platform solution." You can't solve it by applying social platform mechanics such as github PRs and/or votes of StackOverflow/Reddit. (My parent comment tries to explain this.[2])