they can't do what we do therefore they aren't what we are

And what is that, in concrete terms? Many humans can’t do what other humans can do. What is the common subset that counts as human intelligence?

Process vision and sounds in parallel for 80+ years, rapidly adapt to changing environments and scenarios, correlate seemingly irrelevant details that happened a week ago or years ago, be able to selectively ignore instructions and know when to disagree

> “I’ll know it when I see it” isn’t a compelling argument.

It feels compelling to me.

I think a successful high level intelligence should quickly accelerate or converge to infinity/physical resource exhaustion because they can now work on improving themselves.

So if above human intelligence does happen, I'd assume we'd know it, quite soon.