I think it is more that you can't build a genuine General Intelligence before you have solved some intractable mathematical problems, like practical algorithms for solomonoff induction.
Why think that you need to use a Solomonoff Induction (SI) approximation to get AGI? Do you mean to take it so loosely that any ability to do wide-ranging sequence prediction count as a practical algorithm for SI?
Well, solomonoff induction is the general principle of occamian priors in a mathematically simple universe. I would say that "wide-ranging sequence prediction" would mean you had already solved it with some elegant algorithm. I highly doubt something as difficult as AGI can be achieved with hacks alone.
My friend, hearing me recount tales of LessWrong, recently asked me if I thought it was simply a coincidence that so many LessWrong rationality nerds cared so much about creating Friendly AI. "If Eliezer had simply been obsessed by saving the world from asteroids, would they all be focused on that?"
Obviously one possibility (the inside view) is simply that rationality compels you to focus on FAI. But if we take the outside view for a second, it does seem like FAI has a special attraction for armchair rationalists: it's the rare heroic act that can be accomplished without ever confronting reality.
After all, if you want to save the planet from an asteroid, you have to do a lot of work! You have to build stuff and test it and just generally solve a lot of gritty engineering problems. But if you want to save the planet from AI, you can conveniently do the whole thing without getting out of bed.
Indeed, as the Tool AI debate as shown, SIAI types have withdrawn from reality even further. There are a lot of AI researchers who spend a lot of time building models, analyzing data, and generally solving a lot of gritty engineering problems all day. But the SIAI view conveniently says this is all very dangerous and that one shouldn't even begin to try implementing anything like an AI until one has perfectly solved all of the theoretical problems first.
Obviously this isn't any sort of proof that working on FAI is irrational, but it does seem awfully suspicious that people who really like to spend their time thinking about ideas have managed to persuade themselves that they can save the entire species from certain doom just by thinking about ideas.