Do people actually know what "not that deep" means anymore?

I feel like some people just spam that phrase anytime they can just to be "cool".

Like, I was just talking to my friends about different types of mythical beings and asking my friend, "Am I just a nerd, or is it not common knowledge that alicorns, unicorns, and pegasi are different races of ponies. And then someone comes along saying, "Not everyone is educated on the difference; it's not that deep."

???? What do you mean it's not that deep? What deep talk was I even doing? There was NOTHING deep about what I was asking, so why are THEY saying "It's not that deep"? Oh my DAYS.

I get that people say "it's not that deep" to be dismissive, but what was that person even being dismissive of? We were just talking about unicorns bro. Is this part of the literacy crisis, that people of this age dont even know what the recent phrases even mean?