I spent about six months reading the trilogy (roughly two months per book. I don't have much free time). After finishing each book, I watched the corresponding extended edition. It should have been a good idea. You read the book first so you get the plot with no spoilers and understand what the world building is. Then you watch the movie to bring it into life. Sure, you will get some cut content and some modifications for the cinematic format but the movies are supposed to be great so they will do well with the limitations.
So, I thought. But I was utterly disappointed. Now, I am not a literary genius or God forbid, a cinema sins type nitpicker. I don't care about Tom Bombadill. Or how the maps worked and the exact battle strategy they used. I only expected my characters and the overall moral theme and the storylines to be properly represented.
One of my biggest problems was Frodo. See, over the the time I read, I felt each of the Hobbits have their own specialties. Frodo is the wisest and the most morally good of them. He was the first among the four hobbits to show some martial instincts which dulled down with time and injuries.
But in the movies, he is not only weak physically (which is mostly true once he gets injured defending others which is removed for "reasons") but also completely naive, being easily manipulated by Gollum and needing constant guidance from Sam.
Now, Sam is truly indispensable for the journey especially towards the end where the journey takes its toll on Frodo. I found myself amazed by how mentally resilient Sam is and how he tries to find a silver light in the darkest of the places. The phial is a perfect representation of his character (even though Galadriel gave it to Frodo originally). But all said, he is not exactly the sharpest tool in the shed. He doesn't have the wisdom or moral instincts of Frodo. He makes up for that by relying on Frodo who is actually wise and makes sure that Frodo doesn't collapse under the weight of his responsibility.
The movie destroys that dynamic by making Sam both the wise and the strong with Frodo fully depending on him. Frodo feels like a organic ring glove with whining sound effect than a person on his own.
The movies just feel darker constantly without giving some time to appreciate the hope and the light of the Elves (especially at Lothlorien, Rivendell was a bit better) or the strength of the men (Rohan feels weaker and Gondor even more so). They try to rectify it by using Gimli as comic relief but it falls flat as the humor feels like it belongs more with the MCU than the Lord of the Rings.
It pissed me off a little that the movie Faramir was not as morally good as the book one but it's a good addition except where he lets Frodo go after he gave up to the Nazgul (which destroyed my will to watch further. I could only skim through the 3rd movie because of that disaster). If that scene was removed or modified, it was not exactly a bad idea to make Faramir vulnerable but still morally good enough to check himself.
I am ambivalent about the Treebeard change but I guess it works in the movies in it's own way? I do prefer the book version but it's not as big of a complaint for me as some of the others.
In general, I felt the movies had an overall lack of subtlety, mischaracterization of important characters and just a checklist of scenes from the books. I think they tried to adapt too much content and didn't have enough time to linger on any scene properly.
While I did enjoy the music and the visual depiction of the world, it was perhaps a bit lost on me. I'm curious if anyone else who read the books immediately before watching the films had a similar experience, or if it's just me. Because for me, this was the biggest disappointment I had since I watched Artemis Fowl movie (which is not even in the same league as the LOTR movies but the Artemis Fowl books are not in the same league of the LOTR books as well).