Eh. That could have maybe been phrased better with less hyperbole. But I don't think he is literally making a prediction about practical life outcomes. I think he A) implicitly classes understanding as a terminal value here and B) is using failure to mean not achieving your goals (in this case understanding). That seems reasonable enough. I think a decent chunk of folks on lesswrong would value epistemic rationality even if it was proven that it didn't make their lives any better along other axes. In any case you can dump the "fail" part from the quote and the general idea about mental models is fine.