I agree that these tags are not needed.
For the former I suggest to retag the two questions (the tag then goes automatically away after a day).
For the latter we might wait for a few days if the question "survives" or not. If the questions should be deleted the tag would be gone too.
For tags that only have a few questions to them, retagging is usually ...
My understanding is that most of the time, someone who asks a question on an elementary topic will not be able to name precisely what the relevant tags are. In such cases, it's all up to more senior users to tidy things up. But then not all questions get re-tagged properly
because there are too many of them,
because not everyone thinks of taking care of ...
Using Data Explorer (SEDE) you can check how has the number of questions in some given tag evolved over time. Here are two queries, one showing absolute number of questions in the elementary-set-theory, the other one showing percentage of all question which have this tag. The latter is taken from here: A statistical question about statistical questions.
Proposal: Add the tag grad-curl-div; make gradient, curl and divergence aliases thereof.
Edit 2: I've revised the proposal statement to Alexander Gruber's (in my view superior) suggestion in the comments. Implementing this proposal poses some advantages over the status quo:
It would (productively) free the > 6k questions about the gradient from the rather ...
Proposal: Remove the tag infinite-dimensional-space
This tag was created by the question Are there such things as infinite-dimensional regular polytopes?, which is currently the only question with this tag. I don't see this tag having much utility.
Update : The tag has been removed from the question, and should disappear soon.