It's also like fluid dynamicist vs quantum physicists. If you're just going to move oil around and put down differential equations, who cares about a solid foundation of quantum gravity and chromodynamics.

Yep. In truth, one can almost never win the argument of, "...but do I really need to know this?" But people should be aware that knowing fundamental things provides insight and advantages.

For sure, but there are diminishing returns. My rule of thumb is that understanding two levels of abstraction below whatever you're doing is usually worth it.