I watched the trilogy's theatrical editions years ago and liked but didn't love them. I wanted to get more into it, so I read the books to have a deeper understanding of the story and watched the extended editions of the films.

The main villain not being a real character is a common criticism from fans. I think it helps to think of the Ring as Sauron and not just the big eye. Every time the Ring tempts someone like Boromir or Frodo or Gollum, that's a villainous act on the part of Sauron. It essentially tortures Frodo by the third film. This doesn't make Sauron a complex or interesting villain but makes him more of a threat to our heroes than just an eye that sends out waves of bad guys. The prequel show that just ended its first season on Amazon Prime, The Rings of Power, shows more of Sauron the character, but most fans seem to dislike the show overall so it might not be worth your time if you don't care much for the movies.

I don't agree that the action scenes dragged. The balance of power in every battle is constantly shifting, the characters are moving around and having to try new things to win or escape, and one-on-one fights rarely last more than a minute. However, I can see how the thirty minute battles are tedious and not exciting if you don't care about the characters or stakes. The scenes with the Ents dragged on purpose as a joke but even fans I know get really sick of those scenes before they're over.

Harry Potter is a contemporary series to the Lord of the Rings (their first films premiered within a month of each other!) and both are the most well-realized living fantasy worlds ever in a movie, so that is a fair comparison. Harry Potter is all about the characters and their personalities bouncing off each other. In The Lord of the Rings, if characters are mad at each other we worry because the greater conflict may not get resolved. In Harry Potter, if the characters are mad at each other even over petty things I worry because I like them and want them all to get along. The only strong character relationships I feel in Lord of the Rings are Faramir trying to please his asshole father, Sam being the best friend in movie history to Frodo, and Bilbo and Gandalf at the start of the first film. Stuff like Arwen and Aragorn's romance and Merry and Eowyn's romance friendship is okay, too.

This is because characters in the Lord of the Rings often are representatives of their entire culture more than they are characters on their own. I didn't mention Gimli and Legolas before even though they have fun banter because they're really just "a dwarf" and "an elf," but the story is about those groups overcoming their differences to stop evil. The equivalent in Harry Potter would be muggles becoming aware of wizards and uniting against a threat. I think this is also why Aragorn is a Numenorean, someone with distant elf ancestry (I think? Help me out LOTR lore nerds.) who can bridge the gaps between them by becoming king of men and technically prince of elves I think (nerds, help me). Even the world itself that they are fighting for joins their side (the Ents). And I think it's really inspiring that the people who unite all these races are four young men from a hick town where everyone parties, drinks, sings, dances, and smokes all day. If Harry Potter is about a regular boy accepting his destiny and becoming the hero he was always meant to be, The Lord of the Rings is about regular people with no destiny and no responsibility becoming heroes anyway, simply because it's the right thing to do.

I also know a lot of fans like all the compassionate, openly emotional relationships between men in the films. They hug, cry, talk about their feelings, and the only man who is concerned about how others perceive him is Gimli, who is laughing at himself by the second film. Compare to the kids in Harry Potter, Han and Leia in the first two Star Wars, or especially the Marvel Cinematic Universe where everyone is so goddamn sensitive about what others think of them.

But to be honest, that's not why I love the movies. I love them because of the production design. The hair and makeup, the costumes, the locations, the sets, the miniatures, the cgi (great for the time, mostly holds up okay), the sheer number of extras in most scenes, the way every shot in the first film looks straight out of a story book before the sequels become gritty war films, the design of every piece of architecture and armor and weapon. I think it's the most immersive impossible world in any movie except maybe the original Star Wars movies. It's just impressive to me, even if I don't really get invested in the story much myself.

I'm sorry you didn't care for it but I hope I explained why I and so many others do as well. Personally, I recommend seeing it again some time with friends in marathon format. That's the best way to experience these. I put on the extended edition of Fellowship as comfort viewing but there's nothing better than shouting all the best lines together or playing drinking games like taking a shot whenever Frodo falls down (you will die).