> * if I instead were to write "They're both really tired. They're super tired. Oh man, they're so tired. They're so tired, you've never been this tired in your life", that would be extremely shitty writing, but it would give you time to ruminate on the information*

You’ve set up a great question. Why is what you wrote shitty writing while what Tolkien wrote not?

The answer isn’t just variation. If you look at what’s been conveyed in his writing that wasn’t with your repetition, you’ll start unlocking what I suspect you know is there but are having trouble describing.