why so many highly intelligent, extremely thoughtful philosophers have spent so much time on a (seemingly) ridiculous discussion?

That has been my exact reaction to most of the "big" questions, with a few exceptions.

As for the "justified true belief" "definition", each word in it is already so poorly defined, you might as well give up on it. My personal working definition of knowledge is the capability to accurately predict the outcome(s) of a certain (set of) action(s). Which probably matches an existing camp or two, not that I care.