The phrase "big whoop" is a sarcastic way of saying that something is not impressive or important.
Sentences with «big whoop»
is over 600 pages long and now locked after going through several different iterations, including «Nintendo Direct Island 2 OT The Legend of Big Whoop.» (kotaku.com)
They don't belong to bad movie obsessives like me any more but to the mainstream, but that's a story and a possibly Big Whoop post for another day. (nathanrabin.com)