This is actually kind of an inspiring thought... once it's turned on its ear, that is. My campaign world is dominated by powerful and imperialistic nation-states, gunpowder, and 19th century technology. The O.P. asks a legitimate question: how could this have developed in a world where humans have to compete with monsters and demihumans for resources, and where monsters are obviously going to create too much chaos and instability for any advanced societies to emerge?
The best answer that I can come up with: it's not likely, so obviously, the humans weren't actually competing with anybody.
Demihumans live in hidden enclaves that might as well be pocket dimensions of faerie (or, for those of you that play the new edition, I believe "feywild" is the preferred term). Elves, dwarves, and hobbits just stay out of the way. And monsters haven't been seen or heard from in three-thousand years of campaign time. Three millennia of monster-free peace, with neither hide nor hair seen of even a kobold -- these beasties have become legend. As far as human civilization is concerned, they do not exist. Think about how frightening even a lowly orc is in a world like that? And once the campaign starts, and the orcs come pouring out of the ground by the tens of thousands, faster than any well-drilled army could hope to reload muskets, that's darned horrific. It even makes common elves and hobbits as mysterious as they ought to be if they're rarely encountered and half-legendary.
So... I like these ideas, but not for suppressing technology and industry in fantasy worlds. They just help to make the nonhumans more fantastic, which is much more useful.