> Nothing explains the lack of development the previous few millemnia.

But it also took many, many thousands of years for us to get to the industrial revolution. And we did not have magic, we did not outsource stuff to elves and dwarves, we did not have wars with orcs and dragons and other monsters and no extremely powerful transcedental/imortal beings actively involved/shaping the development of history.

And we only overcome feudalism because of the plague and the discovery of the New World -- non of which happened in the LOTR universe.