I think the real value of KSP is orthogonal to textbooks. Like it says in that one xkcd strip, it gives you an intuitive understanding of orbital mechanics by letting you interact directly (and with a goal) with orbital trajectories. I think you'd have a hard time getting the same visual intuition about how the ellipse stretches and rotates depending on whether you burn retrograde or radially out from a textbook.
The great value, here, I think, is that you can have a process completely alien to humans and get an intuition of it about as good as what we can get from playing around with a ball. In high school physics, ballistics (and therefore gravity) is taught using a ball being thrown in the air for a reason- most people have this sort of intuition for that process, and find it easier to get from there to the mathematical model.
Before games/simulators like KSP, the only way to get an intuition of orbital mechanics like that would be to simulate it in your head a bunch, arduously.
I think this is a potential great source of value: games/simulator can give you otherwise-very-hard-to-get intuitive knowledge of (models of) subjects. Not a replacement for the maths and the crunch, but would probably make it easier in a revolutionary way.
I wonder if this is already happening? There must be a generation of aerospace engineering students now who have sent rockets to the Mun.