Hot take: The movies are better than the books. They keep almost everything that was great while cutting out the shit.
For everything they did good, they did bad. And I love these movies (Fellowship is my favorite movie ever).
No Barrow-wights and Tom Bombadil -> no elvish blades - > doesn't make sense that a hobbit stabbing the Witch king would do anything. Maybe nitpicky.
The extended "frodo is dead" and Mordor piece of ROTK is great in the books. Sam as a fearsome elvish warrior, sneaking around, etc.
Frodo giving Sam the boot and believing Gollum on the climb up the mountain. Lame.
And the biggest, no Scouring of the Shire. There's a point to the end - where they come home from war only to find the fascists...ahem...I mean, Saruman... has taken over Hobbiton and turned some hobbits bad and the evil is starting all over again. And then the adventure-hardened hobbits kick his ass. There's so many strengths in the original ending and the movie would have been better for it. I get it is hard to do in pacing a big movie but it could have been done, I think.