Neonchameleon
Legend
I'm going to misinterpret your point here and run with it, so bear with me for a moment.
Although Vancian magic does not mechanically match typical fiction, it matches the feel of older classic fiction. That it, powerful magic is something that is only available sparingly. It takes a lot of effort to cast a spell, and after you cast it once it would be extremely rare to see it cast again any time soon.
And this to me is where D&D Vancian casting fails utterly and thoroughly once you reach AD&D 2e. "Once per day" is not rare unless you happen to live in Fantasy ing Vietnam or be playing a small commando unit, fast moving and hard hitting and on a mission to loot all you can - and never spend the night (or if you try you get hit by a wandering monster roll every ten minutes).
Gandalf might not spam spells - but he would if he was an AD&D mage. How many fights does the Fellowship get into in all the weeks it was travelling? The only time it's more than one in a day is IIRC Moria. So other than Moria in D&D he would have a full loadout of spells. The 4e Bladesinger would be a better match for Gandalf - with only four daily attack spells at level 30 and the rest of it being either minor magic or bladework.
And as for characters like Jadis who barely cast at all, they are not AD&D Magic Users. AD&D magic users are more like Harry Potter - able to scream Expelliarmus half a dozen times in a day and still have half a dozen other spells at mid level.
On the other hand inside a dungeon the 1e spellcasting rules work the way you say. Outside they fail miserably. It's an easy tweak - Wizards need to be in a secure environment with a library and clerics in a church to regain any serious magic. But it's not a tweak that's part of D&D, meaning that the second D&D wizards stop dungeoneering they stop behaving anything like the fiction.
I'm not sure the fiction would change. Most D&D related fiction I've read (and that's a lot) skirts around the distinct prepared casting slots and memorization parts. The wizards have just the right spells prepared mostly. If the Spellpoint system would be default but the spells and accessible spell levels stay the same I think you'd still recognize it as D&D.
Indeed. Vancian casting doesn't even simulate D&D fiction very well. That's how bad a narrative fail it is the second you take it away from dungeoneering.