Fighter could lose their armour, rogue their dagger, wizard their spellbook.
In any case, I certainly don't want the old school paladin trapping, where the GM creates situations where the paladin is likely to break their oath. But if a cleric openly and knowingly went against their god in a big way, then yeah, I would make them lose their powers. Granted, the only realistic scenario I could imagine this happening in my game, would be the player intentionally setting up a class or subclass change. But I like the fiction of there being a constant metaphysical connection between the cleric and their deity, it being an act of channelling the power of the god rather than the cleric wielding the power on their own right. To me that is what sets divine magic apart from the arcane, and I like to have that distinction.
I'm sure you know it's not nearly the same situation. The wizard is definitely on the side of "lose your spellbook, lose your class abilities" like the Paladin. But the fighter or rogue just needs to pick up another weapon or dagger, of which there will be plenty. The Paladin loses his abilities due to a ruling that they have broken their oath, and there is no picking up another oath off the ground.