Some of those really bug me too. The little things like stupid jokes more than the big things like character changes, honestly. I adore LotR; it’s been a favorite since childhood. But there’s very little character development. It’s essentially a milieu story. That sort of works in a book but it really doesn’t work in a movie. Movies need to be character or event driven. So in order to make the movie work, they inserted character changes.
I don’t like a lot of those changes. Aragorn’s particularly bug me. But it did give Aragorn growth as a character. He had goals and fears. Original book-version Aragorn... didn’t.
Some of it’s hubris, the filmmaker thinking he can tell a story better than the author. Some of it is translation difficulties. And we as viewers have to decide how much altering of the source material we can take. There will always be some. I know exactly how Smaug looks and sounds and the movie version will be wrong, guaranteed, but I expect to enjoy the movie anyway.
Somebody who has spent 60 years working towards a goal just may have done all his "growing" already. Portraying this guy at his time of life as essentially an insecure twenty-something was insulting to the audience's intelligence.
If they had to have "character growth" it could have been handled via flashback. Five minutes of flashback showing Aragorns's life would have given plenty of room for character development.