The industrial revolution is in the book, it's the actual antagonist of the story. Tolkien was a devout Catholic distributist and Hobbingen was his ideal Catholic community of self reliant Hobbits who answer to wizards and kings, not to factory floor managers and administrators.
This. Also, there are a few moments scattered throughout the book where the hobbits get to eavesdrop on conversations between Sauron's orcs and we gatch a few glimpses of Mordor's internal organisation. The tone of those conversations always struck me as surprisingly "modern" compared to the "epic medieval" style of the rest of the book: Orcs apparently have ID numbers, they complain about arrogant bosses, at some po…
The wars in the previous ages are described as being a bit more “equal” suggesting there were equally large hosts of humans/elves though, but maybe they’re able to organize “because magic” (e.g. elves may benefit from lembas bread allowing them to not have to worry about supply lines like the orcs).