Let’s just get rid of peer review
All that goes to say, if you just one day got rid of pre-publication peer review entirely – just got rid of it, full stop – there’s no reason to believe that the overall quality of published research would go down, at all. You’re still incentivized to publish your best work; arguably more so because you no longer have the cover of “being peer reviewed” as legitimacy. There will still be good research, and bad research. And post-publication peer review will still be able to pass judgement on anything it wants.