Since the beginning AMP team was clear that AMP is not very useful without cache.
I do agree with all of the concerns raised, but wanted to point this out as to not get sidestepped from the main discussion.
I don't see that at all. Even just calling it a "specification" is misleading in the worst ways. You don't need a spec for caching. Nor do you need a spec to tell you that you shouldn't include a ton of CSS and JS. Nor was it ever the plan of Google to actually see others implement this spec.