The above-linked question ended:
With that being said, I hereby propose that we lock the "good" open-ended puzzles for their historical significance and close the rest.
Perhaps getting rid of the "open-ended" tag would be in order as well?
That didn't happen.
We have a bunch of open-ended puzzles lying around. Occasionally someone adds another answer, further demonstrating why these questions are off-topic. There will never be a provably optimal answer, so more answers will keep coming. And coming. And coming. Along with votes every time the post hits the first page, giving the impression that these are accepted, on-topic questions.
But they're not. We decided that. The tag excerpt says:
OPEN-ENDED PUZZLES ARE NO LONGER IN SCOPE. Used when no answer can be guaranteed to be the last, best one. If a puzzle instead has a provably optimal solution, tag with [optimization].
Is there anything we should do to clean up these old broken windows? I personally started looking through these recently, but I realized that this is a big project and shouldn't be undertaken by a single user without a chance for open input.
So I'm asking for input. What should we do with old open-ended puzzles?
I've posted an answer below. Please vote and add other answers/comments as you wish.