Code reviews seem like a hellscape of "could do X".

Like man it's code, there's an infinite amount of "could do" with an infinite amount of contexts.

I found google's advice to be pretty good https://google.github.io/eng-practices/review/ while they give a lot of good advice / suggestions, they also make a point that there aren't a lot of hard stops and generally if the code works and isn't horrendous you let it go.