But it does have its effect on a fantasy Gamelit world.
It's not just shoving the gods off stage. All sorts of celestial beings -- and infernal as well -- need to be rare, numinous, and mysterious because of their metaphysical connotations. This means, of course, that you can't just summon them. Summoning natural animals, monsters, and possibly elementals is another matter -- because they do not need to be of the forces that govern the universe. Familiars would have to be real animals, not spirits disguised as them. Familiarity and mystery do not play nicely together.
All the spells that involve going to a plane of the afterlife are out. So are a fair number of necromantic spells. (I read a gaming supplement that said that the number of elves is fixed, every newborn elf is a re-incarnation. Imagine an elvish culture with low fertility meeting one with high fertility. The first accuses the second of stealing all the souls; the second, the first of being selfish or lazy or accursed and promulgating the fixed number of souls as an excuse. It really matters whether the characters can establish that one side or the other is dead wrong.) Probably the only spells to raise the dead -- if any -- would have to work within minutes if not moments of death so the revived don't know too much.