I hate when people praise Lord of the Rings. And the worst part is, everybody does. Lots of published novelists make broad claims about the way fiction should be (eg. all villains should have at least one redeeming trait), realize that Lord of the Rings doesn't meet that criterion, and then make up some stupid exception for it (eg. "but that was then, and this is now" - I've seen that one verbatim before). Well I'm sick of it. You're about to hear all of the reasons Lord of the Rings is trash.
Boromir was right when he said, "Give Gondor the weapon of the enemy." Power is not evil and goodguys need to use it to beat people who are. I know the one ring is a special case because it causally corrupts you, but that's metaphysically impossible because nothing can take your free will because free will is immaterial. While you could argue the ring only simulates this effect by subjecting the wearer to extreme temptation, there still should have been a question of trying to resist it instead of sacrificing millions of lives to win the war the hard way. Especially since Frodo slipped on the ring at at least one point during the story and wasn't corrupted.
The way evil is portrayed. In Lord of the Rings, the badguy is just another evil overlord who wants to burn and destroy and kill and enslave for no reason. That's not what real evil is like. But perhaps more dangerous is that he's presented as something outside of human society and that wants said society destroyed/enslaved/whatever. But real evil isn't like that either. Real evil comes from inside human beings that probably seem normal and nice on the outside. Depicting evil like they do in LOTR is dangerous because it makes us feel that all humans are basically good and the only evil we have to worry about is external, insentient forces trying to destroy us. Precisely the opposite is true.
Monarchy is portrayed as righteous. Enough said. I shouldn't even have to go into Anarchism to explain to the average reader that this is messed up.
It might be surprising that I listed this point below the second one when it's clearly more important. I did that because positive portrayal of monarchy is such a common thing in fantasy fiction that I think each individual instance of it doesn't do that much damage any more.
The story is quite racist. I don't mean against black people (although it's arguably that too), I mean against orcs and uruks and goblins and to some extent against dwarves and humans as well. There are several scenes where the three 'evil' races are shown talking, which presumably means they're sapient, and yet Tolkien leads us to believe that members of these species are inherently evil. Out of an entire race of sapient beings, there would and should be at least some good orcs/uruks/goblins in the world. It works in the opposite direction too. Can you name a single bad elf in the story? I can't. Also what is it about humans and hobbits that make one somehow inherently more vulnerable to corruption than the other? Like hello, none of this is possible because our moral inclinations have nothing to do with our biology.
Nothing about the magic comes close to being explained. We have no idea what Gandalf and Saruman can and can't do except for the things we saw them do, which wasn't actually very much for how powerful we're lead to believe they are. Everything they did do with it hit me as a huge "What? They can do that? How does that work?" Cases in point: Gandalf's resurrection, the Witch-King's breaking of Gandalf's staff, Gandalf's breaking of Saruman's staff...
The protagonist is totally disinteresting; he has no arc and no distinctive personality. In fact that can be said of all the characters.
An extreme shortage of female characters. It's been years since I've seen the movies, but if I remember correctly, there is a single combatant woman (who fights once) when virtually every man is the story is a badass warrior, and about one other woman (Galadriel) who is in about one scene. (Let's not even talk about The Hobbit...)
Also, despite the misogyny, Tolkien somehow manages to fit in some misandry as well: the scene where Eowyn (is that even her name? Sorry if it's not) says "I am no man" before killing the Witch-King. Goddammit Tolkien, did we really need that?