QKEs have nothing to do with quantum algorithms running on quantum computers. Also they don't solve any real problem, but that's another topic. It's an extreme

QKEs have nothing to do with quantum algorithms running on quantum computers. Also they don't solve any real problem, but that's another topic. It's an extremely impractical and expensive way to implement a key exchange over short distances which, as you said, is vulnerable to mitm attacks. I don't know why anyone would want to have that.