> So far there is no evidence that this is actually doable over anything but billions of years (and even then we have no idea how nature really managed it).

"The brain is so mysterious and unique, that we should abandon all attempts to even try to apply results like the general approximation theorem to it and discard all signs that some approximation is happening."

Why we don't see signs of intelligence in the universe? The simplest self-replicator requires accidental synthesis of the sequence of 200 (or so) RNA nucleobases.

BTW, your argument could have been applied word-for-word to powered flight in 1899. In short, argumentum ad ignorantiam.