The ultimate goal of any answer should be to solve the problem that the asker is facing. Sometimes that involves not going to what they directly wrote, because sometimes that's not the most effective way to go about it. For much the same as there are people who can't use alternatives, there are people who didn't think about the alternative options in the first place. It's very easy when some askers run into a problem, to tunnel-vision that "I must solve it this way" and then someone provides a very enlightening view by working outside the box the asker had situated inside.
That said, this is also part of the very nature as to why these sites permit more than one answer to a question. It is to allow different routes to solve the same problem. Some will be the direct route that is asked, others will take shortcuts as they see fit.
It remains though that naturally, sometimes an alternative, be it a particular one or just in general, is not permissible. When this is the case, that kind of a restriction is part of the problem. As such if the asker can't work with a given alternative, and if the only answers they're getting is that alternative, it's to them to modify their question to exclude that alternative as an option. Or if it is a known quantity to begin with, a pre-emptitive exclusion present in the question when asked is very appropriate. On the other side, if a reader happens upon a question and cannot utilize the alternatives that exist there, then they are welcome to recreate the question in a fashion which excludes the alternatives since their situation cannot cater to it.
Sans such an explicit exclusion, if the asker can work with the alternative, or if they still receive other answers that do not employ that alternative, there's no foul going on as a result. It's fine to dislike something being provided as an alternative, but it's by no means something we're going to discourage on a level to the point of flagging. Downvotes, those are yours to give as you see fit to things that you believe are not helpful - I could say something like "It's probably more appropriate to downvote if a particular alternative is actively unhelpful to you, as opposed to a post which you stumble across in random browsing which just happens to be an alternative", but at the same vein, you could still deem it unhelpful and the vote is yours to cast. Just be open to the fact that if the alternative does work for other people, it's going to remain acceptable on the site.