[...] I find this sort of "don't even try this because it's a stupid idea and you're going to fail" attitude extremely harmful. That's not what the author had

[...] I find this sort of "don't even try this because it's a stupid idea and you're going to fail" attitude extremely harmful. That's not what the author had in mind. In fact, it's explicitly written: "[...]or alternatively, that they are unsolved problems that someone, someday, somewhere, may actually come up with a variant that hits big." So, it's rather "If you invest serious resources in that, you better know why exactly you're better than the gazillions other guys who had tried this." than "Don't try at all". And yes, trying those ideas as a sort of training is a brilliant idea in itself.