Even the LOTR adaptation is questionable. Gandalf kicking Pippin (the exact opposite of what happens in the book), the lack of the scouring of the Shire, and super-Legolas right out of a Marvel movie...
I have a lot of criticism for some of the plot changes that jackson made but I'll credit him for this: his films are the first dramatic sword & sorcery type movies that got the tone right and aren't cringe worthy. The previous attempts at LOTR are awful.
There was Conan the Barbarian before them. But pretty much everything else in the genre was mediocre or cringe-worthy.
On the other hand, I remember fondly the movie nights a local sci-fi club used to run until the mid-2000s. There were so many terrible Conan clones that were enormously entertaining. And there were some brilliant moments in the early LOTR movies. Such as "Where There's a Whip".
Conan the Barbarian: co-written by Oliver Stone, directed by John Milius, music composed by Basil Poledouris. Oh, and co-starring James Earl Jones and Max von Sydow. An astounding lineup.
The LotR movies were a high water mark, even if they aren't perfect. I wish Peter Jackson made a movie for Children of Húrin, though that's probably not happening for many reasons.
The LOTR movies are great movies, but are pretty poor adaptations. I don't mind changes which were necessary due to the medium (e.g. cutting Tom Bombadil, which just would bloat the movie without adding anything crucial to the story). But Jackson went beyond that and made changes (for example, having Faramir give in to the temptation of the Ring for a time) because he disagreed with Tolkien's story (that specific change was explained in terms of Faramir's character in the book "doesn't work with the way we are trying to portray the Ring"). That's crossing a line, imo.
The Hobbit movies, on the other hand, are both bad adaptations and bad movies. Truly awful stuff.
I think what Tolkien would have hated the most was Aragorn murdering the Mouth of Sauron. Stylistic choices are one thing, but turning morality on its head is on another scale.
This is wildly unrelated and I apologize but it reminds me of Apollo 13 vs From The Earth To The Moon (which Tom Hanks directed so one suspects he had more creative freedom)
FTETTM has artistic license. There's no record of Collins (Apollo 11) saying "If you had any balls, you'd say 'oh my god! what is that thing?', scream and cut your mic" but it's very in line with his general character, you can imagine it happening
Apollo 13 put in a bogus argument with Swigert after the oxygen tank exploded
I will never not despise "artistic license" which is just simply wrong