I play since classic and I never liked to cast fire spells as a frost mage, in fact one of the changes I liked the most recently was the fact that every mage spec got its own "armor" spell instead of all mages casting frost armor. I also hated frostfire bolt with all my strength, I'm so glad we got rid of it.
I don't think the amount of abilities that a class has makes it good or bad, class design of Legion was nice and it didn't have 50 abilities