I was today years old minus maybe a few months when I learned this, and I had seen it referenced so many times.
This one is not particularly new. I wanna say that GOAT was new in the early 90s.
But not widespread until recently. I'm a 90's kid and I only remember it being used for sports superstars and such.
I was not commenting on the vintage of this, I was commenting on my ignorance which is where the parent or grandparent comment started from. Sorry if it did not come out right