One of the big things about D&D is to emulate stories. They are the inspiration behind D&D. The whole reason appendix N exists. You can’t divorce the two as easily as you suggest. Also,as mentioned earlier, outside of a paragraph that says HP are abstract, literally every other part of the rules, and how every combat session is narrated, treats losing hp in battle as actual wounds. Language use is important. So treat them however you want, but this attitude that people are wrong for treating or wanting to treat hp loss in battle as wounds, or that people who have issues with super fast hp healing to full after 8 hours are wrong, needs to stop. There is a mountain of supporting evidence that supports people feeling that way.
Yeah, except that they have to be separated, because you can't run the game like a novel.
For example, I read a book series a few years ago (I believe the first book was
Rhapsody) where the three main characters spend a good third to half of the book walking through a dark cave and talking. They encounter no one, they fight nothing, they see nothing, it is just them traveling a massive distance, underground, and getting to know each other.
In a book, this works (actually surprisingly well, the author did an amazing job of keeping my interest with their dynamics despite nothing else going on) but if I tried to run a campaign where even a single full session was set up that way with them moving through a dark, featureless cavern with nothing to do except talk to each other, would it be fun?
Or, how about when we take directly from some of the inspiring myths of Western Mythology and have an unstoppable hero who is multiple times stronger than any enemy or ally, whose ally's are really just symbolic scene dressing for the hero being epic and cool. Think that game would work out? It makes a great story, but having a single person hog all the attention, glory, action, and fun doesn't work in a team game.
The two mediums create entertainment in different ways, because they have different mechanics and different goals. You cannot compare them 1 to 1 and expect to get anywhere.
The concept of only being able to do so much magic within a given time is sound, if only because were magic to be unlimited in a setting that setting would quickly become unrecognizable from anything we can relate to - for the short time it existed before self-destructing, that is.
So, the question becomes how to quantify those limitations; and while neither slots nor spell points (I've used both) is a perfect answer by any means, they'll have to do until a better method comes along.
The other option, of course, would be to do away with spellcasting classes entirely; but somehow I don't think that idea's gonna fly very far.
Yeah, I get they are a "best workaround" for right now. But the fact that you can't combine them, or break them apart, and gaining them seems incredibly odd and mechanical if looked at through a lens of story just bothers me when I try and make a world using the rules of DnD.
At least Hp work in a way I can model.