Is “human-level intelligence” a meaningful concept?
Yes, in many cases.
Humans have built an advanced technological civilization, and chimpanzees haven’t. There seems to be some sense in which chimpanzees aren’t “on our level,” even though chimpanzees communicate with each other and use tools and have many impressive skills. So there’s use in pointing at humans and saying “that level,” even if there are some issues with using human intelligence as a yardstick.
If we met an alien civilization someday in the depths of space, even supposing the aliens were about as technologically advanced as us, the aliens might be worse than humans at walking and better at swimming. They might be better at adversarial games like chess or poker, but worse at abstract math. Or vice versa, depending on the aliens. The aliens might think slower but have better memories, or think faster but with worse memories.
Who’s to say if those aliens are “human-level” intelligences? (And why not ask if the humans are “alien level”?)
When we speak of “human-level intelligence,” we are trying to talk about whatever quality makes humans capable of building and maintaining a technological civilization, in the way that chimpanzees can’t.
Speaking historically (or rather anthropologically), it looks like at some point after humans and chimpanzees started diverging, a threshold was crossed. It’s not that humans have all the best scientists while chimpanzees have mediocre scientists whose papers keep failing to replicate. The chimpanzees aren’t even writing bad science papers. They’re not writing at all! Human brains and chimp brains are pretty similar biologically, but there was some threshold humans passed such that we could invent civilization and smelt iron and send rockets into orbit and write and read.
To the naked eye, leaving aside all theory, it looks like some kind of dam broke and unleashed a vast flood of intelligence behind it. Some unknown kind of “all hell” broke loose.
There are people who will cleverly object to this idea, but they have to do it by throwing around quibbles and definitions rather than by saying, “Actually, I have uncovered evidence of Homo erectus trying to build nuclear reactors two million years ago; they were just very bad at it.”
Intelligence powerful and general enough to create a civilization seems to have hit the world fast and hard, cleanly separating Homo sapiens from the other animals. We’re certainly not attached to the specific label “human-level intelligence,” which has plenty of issues. But whatever we call it, it’s useful to have some kind of concept for “things that are on the other side of whatever that threshold was.”