Agreed with most that has been said. It’s underwhelming in VII and I feel it’s actually pretty satisfying in VIII, but it’s VI, XII and the job class games (sans X-2) that really make magic feel satisfying.

Also, personally, I like it when magic growth is separate from regular level growth. Makes it feel more mystical and in games like XII, it’s actually satisfying to hunt down those last remaining spells in some dark dungeon. I love IV as much as the next guy, but interesting magic is not something that comes to mind when I think about it