"Brilliant" has long been the British equivalent of our saying "awesome" or "tubular" in the 80s. So used for inanities, used to mock such inanities, then used in defiance of such mockery it has become a space filler in British pop culture.

When it's used in the U.S. as a weird cultural sophisticate affectation, as I've heard it twice at lunch during a business conversation between strangers today, it buries the usefulness of the word for maybe half a generation. Gag me with a spoon.