A big difference between Princess Mononoke and LOTR is the role of society in the narratives. In Mononoke there's multiple competing societies (Ainu, Iron Town, forest denizens) with different and conflicting interests. There's corruption (figuratively) in Iron Town and corruption (literally) in the forest, and the resolution is the excising of these corrupting influences as well as the establishment of harmony between the societies.
LOTR, due to the mythopoetic nature of it, is about Good triumphing over Evil. There's also elves, but they're kind of neutral (well they weren't neutral in the films but they were non-interventionist in the books). There's individual evil and corruption, like Saruman and Denethor, but nothing like rights or society for orcs and goblins despite being ostensibly sentient. They're slaughtered without mercy, they have no motives except for conquest, no agency except to be killed by the Good Guys. Peace arrives at the defeat of evil and the return of the King (to a prior status quo of enlightened mystic kings).
The book is more complex than this but the film wasn't.
