The existence of bad measures doesn't preclude the possibility of good ones, even though they won't be perfect. BAU activities, e.g. devops, can be measured in useful ways[0] as well.
Oh yes. But intelligence needs to be applied. OKRs turn measures into something like a sport, like soccer where those measure become the goal (beat the KR and get a bonus, or even just pressure on the KR and nothing else).
No, I don't think that's true. People might do that, but they also do that to things that aren't OKRs. It's great to critique OKRs, but not by comparing them to a hypothetical perfect world.