I stopped going to BK years ago for that very reason: I never knew what I was going to get, and it wasn't worth the risk.
McDonalds, by comparison, does not even have a great burger. It's mediocre. But it's consistently mediocre. You know what you're going to get. I even like the occasional Big Mac (rarely, but sometimes yeah). I'll choose McDonalds every time over BK because I know it's a safe bet.