My mother used to say, "If you can't say something nice, don't say anything at all." Same thing applies here.
Never do something wrong just because you can't do it right.
This applies to reviews, to commenting ("I would comment, but I don't have the rep"), to sockpuppets ("I had to make a new account because the old one got blocked from asking questions"), etc, etc, etc. If you know the correct action in review, but you can't take it, either Skip (if you're likely to be able to handle at least some other reviews correctly, such as in First Posts where running out of flags doesn't necessarily happen at the same time you run out of votes) or, yes, stop reviewing. Or sometimes you can add a comment to let others know what you think about it, then Skip.
This is especially true of blatant spam; there's no reason to allow that through, and hitting Needs Editing leaves it on the site longer and requires more people to handle it. (Worst case, since this is Triage, it would pass it to the Help & Improvement queue.)