We have gone leaps and bounds since we started building an "artificial brain". Look at where deep learning is leading to. Ofcourse, we can't mimic the brain in all its majesty anytime soon but short of that, there's so much we can achieve.
i don't necessarily disagree with your conclusion, but the argument is that a computer is a different thing to a mind. So, even if a really powerful computer could convincingly mimic a mind or otherwise achieve a similar result it would still be a different thing.
For me a good way of thinking about this is the discovery of genetic heredity. Heredity was known for a long time before DNA was known. Eventually evolution became understood too. But, before DNA was discovered we didn't know what a trait "looked like" in much the same way as we don't know what a thought or memory "looks like."
Without that knowledge it's hard to know if a computer is mimicking a mind or being a mind.
