I really only use "Looks OK" when a question or answer, truly, could not be improved by me, or the improvement would be less than the minimum character requirement for a suggested edit (not quite at 2k rep yet!) I very much urge other reviewers to do the same. Really, just do your best to make the post better than you found it. Simply smacking "Looks OK" doesn't help anyone.
Though I'll also mention that in cases of a question being off-topic (enough that it cannot be salvaged), or an answer being a blatant non-answer, I don't attempt to improve it in any way, and instead I just flag for closure/deletion. I feel that, by suggesting an improving edit in that scenario, I'm just putting an extra burden on reviewers as they'll not only need to help review the post itself for closure/deletion, but now also my suggested edit on a post that needs more post author attention than reviewer attention. If I was over 2k reputation, this would be a bit of a different scenario since all I'd be doing is consuming my own time.
A bit of an outlier would be this review of mine, where this revision was visible. I... Honestly could not understand what was trying to be conveyed there, so I just flagged for closure as needing details/clarity, and threw a Share Feedback comment at it. Someone else certainly needed to edit that (and you and Timmy Jim certainly did), but I did still have actions I could take in review (flag for closure + add a comment). A similar review of mine can be found here (requires 10k to see the deleted content) where I left a comment and flagged for closure as I felt that the improvements I could have made would've been minor enough that I felt the onus should be on the post author to improve the question before I attempt to make any improvements.
Often I'll review a question that you have already improved (considerably, in fact!) Here's an example. You sure do like to make things easy for me!
Something you may already be aware of, but others might not be, is that the access to moderator tools privilege comes with the ability to review the full review history of each queue. By navigating to a particular review queue's "History" page (here's First questions' history), you can see the full history of reviews on the site by all users, and as a grizzled veteran of the site, you can ensure that what happened during them was correct. If they weren't, you can correct them by navigating to the post and adjusting them.
If you notice a worrying trend of a particular reviewer taking incorrect actions during review, flag a post (really any works, I like to choose one of my own) for moderator attention and link to all related reviews, and ask that moderators issue a review suspension. If you are running out of space in the flag dialog's explanation box, see this wonderful answer by Ryan M on how to shorten your links so that you can fit more text into the dialog. (View the latest revision's source to see the markdown used.)