I think it's a Trap
A piece of tagging theory which isn't invoked very often, and which is hard to apply directly to things, is that we're (generally) tagging for concepts as opposed specific in-game content pieces. It's just that very often D&D's name for things is the de facto name for the concept. Or that a different game system's name becomes a name for the thing.
Wishes and Simulacra are things onto themselves to a greater extent than which glyph of warding really is (I'll get back to that). And related to spells and our tags, it's just that D&D (and by our extension most of our questions) implement those concepts as spells. D&D implements quite a lot of stuff as spells. I will admit this is close, and worth a full consideration, but I'm landing on not quite.
I'd like to bring you along with the journey I went on. I started out being for the tag, for pretty much the arguments laid out. However, applying the above notion to 5e's symbol spell should also fall under the same tag as it's doing basically the same thing. And that's where the tag name fell apart for me. While no one is gonna bat an eye at a question about limited wish is tagged with wish, tagging a question about symbol with glyph-of-warding seems wrong. Much too artificial.
But is there a better name? Well, the short description for the effect would be spell trap, which would make a fine tag bar two things. Firstly, we don't like inventing our own terminology. The second is that we already have that covered. spells traps as a combo should cover that perfectly.
And I'm aware that glyph of warding has some uses which aren't strictly as a trap (how much of that is for actual play and how much is theory-crafting I can't say). If the traps tag is wholly inapplicable, leave it off. Tag the question with what it is about. If it's purely about the spellcasting process, tag it with spellcasting; if about creating a permanent effect, permanency. But often I'd think a question about using a trap for something other than its original purpose is still about traps, magical or not.