With the martials I can agree, with the wizard in particular imo they'd need a lot more time than they really get in most campaigns for studying, their level up spells IIRC is supposed to be the stuff they get from experimenting during downtime but the game doesn't really show downtime training at all. I'd rather most classes have to show putting more effort into training either way tbh, for martials it'd be training new techniques before they can do it in combat, for casters it's new spells Even a sorcerer should imo have to spend some time learning how to use their powers in ways they want them to.
In the playtests of old Warlocks were intelligence casters and some of the flavor stayed. Made more sense to be a researcher that strikes a deal for knowledge while a charisma one would be more inclined to bargain for straight up power.