39th lv DM
I disagree on the warlock since the class is all about patrons & pacts. If making a deal for power with some entity like a Great Old One, Arch-Fey, intelligent weapon, "darkness" etc isn't a function of Cha then I don't know what is.Intelligence is important for the Wizards. Anyone wizard-like should need some degree of mental capacity, memory, and reason. This is actually one of the most UNDER-served abilities in 5e. Warlocks, certainly, at the least, should be Int.-based casters. Sorcerers can still be "Charisma-casters"...but Intelligence should be important to them to. Being able to understand how to work magic (arcane, at least) should be an intelligence thing, by definition.
After that (spell saves, attack/damage mods, etc) it's just a measure of how much power you've been granted. And like a sorcerer you don't neccecarily need to understand the power, just channel it.