Uh, what?

In finance and economics, the greater fool theory states that the price of an object is determined not by its intrinsic value, but rather by irrational beliefs and expectations of market participants.

By definition... the problem disappears if actors are rational. This is not a contentious matter of argument. It's in the definition.

Not really, unless you mean it in some sort of religious sense. You still have information asymmetries, power asymmetries, different priors, and bounded rationality. Plus the inherent limitations of any system of decision making.