TL;DR My view is that if Einstein hadn't proposed his theory of relativity, someone else eventually would have (especially as the evidence for it accumulated) though it probably would have taken several decades. That is, "1.8 Einsteins" is an accelerator, not a possibility-maker - in the same way that 1/10 Manhattan Projects is an accelerator (and we've spent many Manhattan's worth on AI already).

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Einstein wasn't the best mathematician (he was good enough to do the maths his physics required, but he needed help and other mathematicians of the time, such as Laplace, were better). What Einstein had was an insight, and an iconoclastic attitude that allowed him to overturn established dogma - far from being a barrier that he had to force himself to overcom, it seemed to energize him.

I think of Einstein as an explorer. To be an explorer, you need to have the abilities of an explorer and the boldness to try to new things. There also need to be things that haven't been discovered yet, but whose existence is hinted at (e.g. Earth didn't seem to be traveling through an ether).

- Without puzzles to connect you to reality, it's very hard to come up with breakthroughs that matter.

- Without an individualistic attitude, you won't be willing to pursue lines of inquiry that everyone else says is stupid and a waste of time.

- And without the necessary ability, you do it; you can't work out the details to show that it's consistent, you can't make predictions that could be falsified.

In Einstein's later life, he didn't come up with further breakthroughs. Was this because his intellect lost the sharpness of youth (so that Einstein himself was now < 1.0 Einstein)? Was it because he became attached to his own dogma (e.g. god does not play dice with the universe) - his biographer, Walter Isaacson thought so. Or was it because there weren't any amazing discoveries within reach of current experimental evidence? (a lot of work was done on quantum mechanics, an area Einstein didn't want to pursue; later theories like string-theory do not explain experimental evidence in a simple way).

I'm not just writing an essay here on Einstein - I'm talking about the basis of scientific progress. It doesn't depend on "genius" (e.g. "1.8 Einsteins"), but on those three things: sufficient ability; attitude; and unknown discoveries being within reach. There's also persistence - Einstein took about 10 years to generalize his "special relativity". A better mathematician could have done this much more quickly, but they didn't think it was worthwhile. He did.

I also interpreted "1.8 Einsteins" as an accelerator, because of the context of 1/10 of the Manhattan Project.

And if you include everything that contributes to better computation (cpu, memory, bandwidth, languages) as well as explicit AI research (though note that once computers can do something, there's a tendency to not call it "AI" anymore e.g. chess playing so that explicit AI research includes more than it might seem at first), then many Manhattan Projects have been spent on AI, with some progress, but without the slightest hint that we are anywhere near within reach.

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As a final point, even if the statistical unlikelihood of a 1.8 Einstein meant that AI was likely impossible for us, why does it follow that you disagree? It may well be that it is possible to understand intelligence enough to create it - but that we aren't intelligent enough to do it.

Most of our intellectual progress proceeds from standing on the shoulders of giants; which usually involves a level of abstraction that makes things simple again (i.e the complexity required for understanding a level in itself isn't cumulative; we can understand one aspect at a time). I personally experience this all the time - the only way I make progress is by forming a theory of a confusing thing, that separates out a level, or an aspect, and makes it simple enough to bring it within my intuitively grasp.

Is it impossible that there are theories so interdependently complex that we cannot separate them out in this way - that there is no component that we can understand in isolation that will help us understand the whole? i.e. irreducible complexity. Note that all our scientific progress is based on things that we can understand. There could be many true scientific theories that we could not even formulate - and how would we know?

Note: I personally think AI is possible, that we will be able to understand it. But I recognize this is an opinion, not a fact.