Well, if you make these big spells with 24+ shifts, after a while, you'll end up with aspects like "focused" and "really focused" and "really really focused", just to somehow make up the discrepancy in shifts. I'd much rather have one cool aspect that gives the spell a shape, a place in the story, that makes it memorable.
I'm not assuming anything (I assume). I was mainly trying to explain my take on things. I grant you, that sometimes gets away from me and turns into a ramble.
The point is, large numbers do nothing to make the spell more interesting. At the very least they are a hurdle, at worst, they keep the spell from getting off the ground in the first place. While all we really want to do is see what cool stuff the spell can do.
The important question is this: "What happens when the spell fails?"
If the answer is "well, nothing, really", then why bother rolling in the first place? When you do a tracking spell, it succeeds, because the interesting stuff happens
after you found the target. If you don't find it, the story kind of grinds to a halt, or at least takes an uninteresting detour that can be avoided.
Unless, maybe, you don't have much time, in which case you might have to roll to see if you find the little girl before the ghoul eats her. Now there's something interesting, you
need those dice to roll well, you can't just take your time. Now we're cooking.
Then there are special cases, where casting the spell isn't really interesting, but putting the spell together is. You need to get the right ingredients, the right symbolic link, etc. Once you've got those, the spell is easy, no roll necessary, but to get them is an adventure all by itself.
On the whole, it's a different mindset than most people are used to from other games. I personally love it, though I am occasionally still struggling to stay on top of it and not fall back into old habits.
See? I'm rambling again. Sorry about that.