The two main modes are, of course, the pastoral Hobbit sections (not just in the shire, but right up to the end whenever we're following hobbits as our pov character you get to hear about day to day concerns of cooking and cleaning and homelife) and the high fantasy style of the Men esp anything with Aragorn and no hobbits (full names given at the drop of a hat and plentiful information about lineages and ancient battles).
But along side this we also get the oral/ lyric tradition exemplified by the Bombadil sideline, the rambling medieval scholar (gandalf reading the half descroyed chronicle in Moria) and yes, the grumblings of modern industrial bureacracy of the orcs and later the hobbits in Sharkey's thrall.
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).
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 point talk about one of the Nazgul's winged beasts like requesting a helicopter flight, talk about setting up on their own, etc.
The talk sounds more like that of a frustrated and cynical foot soldier in a modern millitary or an employee in a megacorp would sound than some medieval thug.
Sauron's and Saruman's architecture is also very clearly industrial - the book is much more explicit about that than the movie: Isengard is described as full of technology, while buildings in Mordor (and later in occupied Shire) are described as barracks and huts made out of bricks, connected by a regular network of roads. And then there is the "new mill" in the Shire...