Of course they’re comparable. You can compare anything you like. Apples to oranges, for instance, or apples to airships, or apples to aliens. Doom to dessert toppings. Have at it. What we’re saying is that calling Doom Eternal an “old-school classic FPS” is missing the point of both Doom Eternal and old-school classic FPSs.
Well, sure. But why wouldn’t you say Doom is an evolution of “old-school classic FPSs”? Because calling something an evolution of X isn’t the same as equating it with X.