an X of all time

A phrase to poke fun at overrated or mediocre things. It can make a person think something is about to be praised if they read it too quickly.
Instead of praising something, this phrase states that the things was one of the things in existence.
The “X” is just a filler and can be replaced by other words, typically “moment.”

“This is an X of all time”
“Magnolia by Playboi Carti is a song of all time.”