In this case, I think voting is plenty for now. I'm not actually sure if the author is trying to suggest something different or not - so I commented too.
As with all things, there's a bit of a continuum. At the good end, we have the perfect answer. Moving along in the negative direction, we pass through the answers worth upvoting, the ones you shrug at, and the answers that are worth downvoting ("not useful"). Coming to the other end, there are the exceptionally low quality answers which merit deletion; at the extreme, these become "not an answer".
So the question you ask is one that has to be answered on a case-by-case basis, just like whether a given answer is worth downvoting. As a moderator, there's fairly little that I will actually delete just for being low quality. Voting is quite sufficient to sort bad answers to the bottom, and even gray out the sufficiently bad ones. If an answer is dangerously low quality/incorrect (food/kitchen safety), though, I'll likely delete it. I'll also be more inclined to delete low quality answers if everything they say was already said better in an older answer.
As always, if you think it's borderline, worth a mod having a look at, feel free to flag - or simply leave it in the review queue so the mods will see it.