An old question may have existing answers with many votes already, so a new answer that's more up-to-date and even more recommendable would start with less votes. It may get better over time, commenting and adding a bounty on the question may help.
However, you could post your concerns and recommendations to an existing answer with the suggestion to edit it: in that case the answer can be refreshed to be up-to-date and a better choice while keeping the existing votes. Especially if the answerer is still active here, that could be a good approach in team work.
Also, you could suggest an edit to an existing answer, or edit it directly showing more recent information: in that case one should know the improvement though. As in the previous option, it would keep the votes and may even stay on top of a list of answers: in that case one should be sure that the edit may be in the interest of original voters and answerer and in accordance with their assessment. Otherwise one better posts an own answer.
In any case, you can post your own answer and add a bounty to get visibility and votes helping to sort answers.
And if you don't know the answer, you can also add a bounty to get a new answer.
While I think adding a bounty to get visibility to work on the existing question and answers would be a very good way, highly upvoted existing but obsolete answers may seem to be in the way to highlight a new approach. In that case, well, you could post a new question, refer to the old question, state reasons why answers there may be obsolete and require in your question, for example, to use the specific new features, so that makes your question actually different so it cannot be closed as a duplicate. (That may happen to the older question then, if users vote for that.) In any case, add links with comments at both places to connect the information.