Per our help,
A tag is a word or phrase that describes the topic of the question.
Tags are a means of connecting experts with questions they will be
able to answer by sorting questions into specific, well-defined
categories.
Tags can also be used to help you identify questions that are
interesting or relevant to you.
As such, questions about whether this tag matches some weak consensus from six years ago are red herrings: we need to ask if this tag will help connect experts to questions that play to their expertise.
For most spells in D&D, the answer is "no." No-one has peculiar expertise in Scorching Ray, becasue there's not much confusion or controversy there. Any questions someone has about Scorching Ray have an overwhelming tendency to really be questions about how spells work generally (e.g. "can I light a candle with it?").
A small handful of spells are just complicated, deeply situational, or both. The 3e Polymorph series of spells and every incarnation of Wish fit this description, and both come up very frequently. I can easily imagine someone following either of those tags, because they do require specific expertise and they do come up all the time.
Simulacrum is harder to imagine fitting that mold. However, that there are 60 questions which could reasonably be tagged with it suggests that it comes up often enough to be worth tagging, and that RevanantBacon is defending it as a tag suggests that he is interested in following it.
So, underall, Simulacrum sounds like it should be a tag.
This comes with a big caveat: I think it's worth looking hard at scope for these spells. Does the "simulacrum" expertise apply to all editions, or is it specific to the 5E spell? The same applies to other spells too: Wish is likely fairly universal (despite the different costs between editions), but Polymorph behaves fairly differently in 3e/5E.