[gushie]

> You are, generally, supposed to put the new answer on the old question

If you're asking the question, you don't know the new answer.

If you're not asking the question, you don't know the answer needs updating as it is 15 years old and has an accepted answer, and you didn't see the new question as it was marked as a dupe.

Even if you add the updated answer, it will have no votes and so has a difficult battle to be noticed with the accepted answer, and all the other answers that have gathered votes over the years.