I think I mostly agree on keeping track of the field, the only thing that's not clear to me is what should be considered "foundational" in an area where most of the exciting things have happened in the last ten years or so.

But don't you think that just discussing ideas ends up hiding a significant part of the complexity of actually getting them to do something? It's true that learning by doing seems rather time-consuming, but wouldn't we consider it strange if someone said that he'd learn about algorithms without trying to implement/use/benchmark them, theorems without solving problems with them, or even coding techniques by simply reading about them?

Then again, I guess you'll inevitably end up actually having to do things in your PhD/job/whatever, but I'm concerned that a lack of "foundational" knowledge and experience can greatly hamper you at some time-critical point of this process.