The movies jumped the shark in Star Trek II; when they decided Kirk that never dropped all charges in "Space Seed," and that planets explode like in Superman... and that terraforming devices can be more powerful than actual explosives.

Just a giant cluster-mess.

"In nearly every aspect, Jackson's choices either were faithful to the book or made sense" 

Except that Tolkien's intention, was that the entire story was about keeping Arwen safe, to restore the line of Luthien; so she couldn't be mentioned in the story except in ing.

But in the film, Luthien just becomes "some elf-maid who loved a mortal and died."

And there's your answer "why..." Jackson was a teenager playing with matches in an art-museum.

>>"Tbf, taking 3 books packed to the brim with lore and condensing it down to 3ish hours is a massive undertaking."

Especially when he doesn't understand the author's intent-- and didn't want to ask the world's top expert, Christopher Tolkien.

So of course it simply became a silly fantasy-film.

Aragorn did not have Elvish blood; Numenoreans were not Elves, except from being of the Children of Luthien (who the movie said was just "some Elf-maid who loved a mortal... she died.")

As for Elvish blood, that was Boromir, from his mother Finduilas; and so Boromir was much like Feanor, in being proud and devoted to his father, and having a desire to become king himself.

Faramir, meanwhile, was more like his father, in being true of the blood of Numenor; and so he saw right through the danger of the Ring-- and its plot to test him, by giving him the option to take it-- and he had every right to do so, just like Aragorn and Isildur.

Faramir didn't need a "hobbit on his shoulder" to tell him the right choice!

In fact, Sam blabbed about the Ring, because he sensed Faramir's Numenorean wisdom.

So Jackson simply corrupted all of the book-characters, in the same way that he missed the entire plot from beginning to end.

He was simply out of his depth.

>>"Jackson had to make a lot of changes to Tolkien's story to capture the gist of it over three feature-length movies."

No he didn't. He just showed that he didn't understand Tolkien's story.

Particularly the Ring, with Aragorn saying:

"We cannot wield it!

None of us can.

It is Sauron's Ring, and answers to him alone."

And then, we get conflicting s about how Gandalf and Galadriel could become powerful by using it, and Boromir wants to use it... but how only Sauron can "bend it to his will."

Meanwhile the film says that Saruman wants Sauron to have the Ring--

which completely misses the plot, since the whole story is about how Sauron only comes to power in the first place, because Saruman wanted to get the Ring for himself.

When in the book, Elrond says that they all indeed had the power to wield it, and could defeat Sauron at any time by using the Ring;

but that they simply could not wield it, without being corrupted by it themselves.

(Which Boromir doubts, thinking that good intentions would keep Men from being corrupted, and that other species were just weak).

And the book expressly says that Sauron fears Aragorn, simply because Aragorn could use the Ring to become a great and powerful lord, and defeat Sauron.

And so when Frodo uses the Ring's power on Gollum, only to make him get out of Frodo's way to destroying the Ring; then Frodo becomes corrupted, and cannot destroy it even at the end, but instead claims it for his own.

So the films give a very vague and confused explanation of the Ring, saying both that they couldn't use it, and that they would be corrupted by it.

But if they couldn't use it to defeat Sauron, then there was real temptation to use it-- and so, no real moral; other than their simply being foolish for believing that they could use it to defeat him, when they really couldn't.

When actually, Tolkien's moral was that they could defeat the enemy by sinking to his level, but then they would become even worse.