The existing answers do a good job with the general situation, but it's also important to touch on a couple of specific cases.
There are several categories of questions, which include
- homework questions, and particularly the blatant do-my-work-for-me variety,
- non-mainstream physics, and
- junk-food list questions,
among others, which the community consensus classes quite solidly as harmful to the site, through various mechanisms. Unfortunately, the review queues are often not fast enough to close those questions before they accrue at least one answer. For several of those classes, there is also a community consensus that the answers themselves are also harmful to the site, because they encourage the asker, and future visitors that see the thread, to post further off-topic questions.
If a given answer falls in this category, is it fair to point out to the answerer that that behaviour is problematic? Yes, absolutely. (So long as it is done in a civil way and following the SE Code of Conduct, that is.) This can take the form of a short comment, a downvote, or a vote to delete, none of which are (or should be) personal, but strictly about the post.
On a slightly thornier side: if a given user repeatedly posts answers in that category, even after having been pointed to the relevant resources that point out the community consensus, is it fair to call out that behaviour as problematic? Frankly, I don't see why that's even a question ─ to me it's pretty obvious that it's fair. That doesn't mean that it the repercussions need to go beyond "somebody told me that X aspect of my behaviour is problematic", though (and it doesn't, unless you're really pushing the not-listening-to-the-moderators over into suspension territory).
And, as pointed out by AccidentalFourierTransform, there isn't a clear line that marks this sort of problematic behaviour, and in that blurry boundary there are plenty of cases where reasonable people can (and do) disagree about whether a post is on- or off-topic and about whether a given question is harmful enough to the site that providing answers to it is problematic. However, the blurriness of the line is independent of the fact that we get a steady stream of clear-cut cases of harmful answers to harmful questions, and those do require community action.
Oh, and one more thing, regarding the thread's title:
[...] long before the latter put on hold as off-topic
Unfortunately, community closures often take longer than we would like them to, whether this be by hours, days or months. The fact that a given question slipped through the cracks and, for some reason or another, didn't get picked up by the community moderation mechanisms, has absolutely no bearing on any of the arguments laid out above.