If you don't know the foundations well, you don't belong in a postgrad program. That's the reality and how it currently works. Undergrad teaches you those foundations.

Anyone can try doing research, even undergrads who half-know the foundations. However, trying research doesn't mean you have the background to do great research or to succeed in a postgrad program.

Let me ammend my statement. *"Anyone who succeeds at publishing research deserves to be in a postgrad program."

Plenty of people in postgrad programs don't know the foundations. It's ok. You are there to learn.

Completely unfair to expect someone already doing research to slog out 4yrs of classes not furthering their career.

You can definitely do research in an area without having a good background on other topics.