TwoSix
Everyone's literal second-favorite poster
It certainly isn't less "mental muscle" than WIS and CHA, though.This is a rather dated idea of what intelligence is, in both scientific and D&D terms. The science says there are many dimensions to intelligence, including things like social intelligence (charisma), and so on. In gameplay terms, the INT stat is pretty much narrowed down to book smarts, with the player themselves expected to supply those aspects of intellect not covered by wisdom and charisma. So, no, the INT stat is not "mental muscle" in 5e.
Like with most of the caster classes, the actual casting stat used should be fungible. Any skill in enchantment magic or telepathy can easily be represented with high CHA; divination and precognition can be a high Wis, etc.