The main idea behind using labels is an option to use LabelSelector on ListFunc and WatchFunc. So it looks like that implementing labelSelector does not contradicts with annotation-based logic in general, but the same logic could be implemented with FieldSelector on annotations. Any way, solution with annotations could be done in this way:

1. Support configuration option like --respect-annotations with false by default for compatibility
2. Add at least main annotation which disables cleanup on exact job/pod kube-cleanup-operator.lwolf.github.com/disabled to disable cleanup for the specific class of pods/jobs for debugging purposes.
3. Support configurable options for jobs/pods delete-successful-after, delete-failed-after
4. Support pods only configuration delete-orphaned-after, delete-evicted-after, delete-pending-after

I agree that labelSelector doesn't contradict annotation-based logic. Merged the PR.

Your plan for the annotations looks great.
The only thing I'd change is the prefix for the annotations: kleaner.lwolf.org instead of kube-cleanup-operator.lwolf.github.com/.