Comment by thaumasiotes

I mostly agree with you. However, if you imagine yourself sitting down with a set of exercises that you need to figure out how to do, it is true that some well-chosen animations / models will be helpful in that process.

You have to do the exercises. But it might be beyond your ability to start doing them straight from the textbook. Crafted didactic material can walk you through initial exercises to the point where you have a theory of where to begin on another one. Or it can let you investigate a structure until you have an idea.

In your analogy, if you want to be able to bench 150 pounds, at some point you'll have to bench 150 pounds. But a nonconfigurable 150 pound weight isn't the best way to get there. You can have a set of weights that let you start with easier tasks. You can have a set of exercises that aren't bench pressing. Those things are helpful, and generally required.