Ovinomancer
No flips for you!
Again, the definition of genius doesn't change in that sentence. It's the ironic use of a word that means one thing when you intend another that's doing the work here. And that work is sarcasm, not the creation of a new contranym*. It's possible you will be eventually correct and the sarcastic use will lose its sarcasm and just become a definition, but I hope that day is far off. That's way much more boring thing than sticking with sarcasm**.You must be fun at parties.
Okay, so now I will be pedantic. As I stated, a typical contronym* is a word like sanction. Here, the word itself isn't a contronym. The contronym is created through context - sarcasm. But you are incorrect when you write that the meaning hasn't changed; the meaning of the word has changed. The form of the word has not.
Why does this matter? Because if you're a descriptivist (as I am), the meanings of the words change over time. So, if enough people start using the word (the meaning) of genius to mean, ahem, not genius, then that is what it means.
It's one of the ways we get new contronyms. Some are accidents of etymology (sanction, cleave). Others are accidents of usage (dust - when used as a verb, are you removing or adding dust?). And others are, well, questionable and evolving (quick, with no other context, is a "classy lady" a lady with or without class).
*I don't appreciate your new-fangled spelling. I will literally die if you misspell contronym like that. Get it? Oh, never mind. It's a moot point!
*[emoji14]
** no sarcasm was used in the making of this post.