I think the most likely outcome is that you’re ultimately going to reach the conclusion that the best option is to leave.

I suppose you could always convert that message to imply a personal standard rather than company policy, and then defend any criticism coming your way as acting in good faith on behalf of the company and its mission to prevent low quality / potentially dangerous PRs.

But yeah ... not as strong an argument if you're stuck with that.

Having said that, if the higher ups are "all in on AI", you may have luck reversing that logic and having an AI filter all PRs on the basis of "quality", where you get to define what counts as quality, as above. You could even have an automated reply to say this PR failed to meet our AI filters, please revise accordingly (and possibly dump either the guidelines or AI-generated feedback on how to correct the PR before it can be seen by a human).

This way you get to tell your higher-ups that you're using an advanced AI pipeline, while simultaneously filtering out (or at least deslopping as much as possible) most bad-quality, generic AI PRs. win-win.