Ok, did we need to hear this rant yet again!?!?
It has so jumped the shark! 
Either that, or we’re old
Because I’ve never heard it either.
The latter is more succinct because it is a common phrase and so is not deliberately exclusionist and does not tempt people to demonstrate their “coolness” or possibly lack of it thereof by using it at every opportunity, warranted or not.
Sadly, I think that the OP was arguing for the use of this stupid ass cliche.
I concur with the poster who denoted the phrase as a favorite of the idiot wanna-be CBG’s of the world.
However, use of “the phrase” does serve one valuable purpose- helping to identify the user as a moron to the other users. Thus that person’s post can be easily ignored or given the mocking it richly deserves.
mmm … 1 point 5 Pie.
Shark, shark, shark, shark. Lovely hark! Wonderful sharrrk! Lovely shark! Wonderful shark. Sha-r-r-r-r-r-r-rk! Sha-r-r-r-r-r-r-rk! Sha-r-r-r-r-r-r-rk! Sha-r-r-r-r-r-r-rk! Lovely shark! (Lovely shark!) Lovely shark! (Lovely shark!) Lovely sharrrk! Shark, shark, shark, sharrrk!
I was going to come in here and agree with the sentiment expressed in the title, but now OG SHARK
“Past it prime” is different than “jumped the shark”. “Jumped the shark” implies a specific event from which you can say it is all over. “Past its prime” does not.