You started a nice thread here,
Leaf!
The problem with the portrayal of Aragorn in those films is partly because he is a difficult character for even avid fans who have read
LotR thoroughly to get to grips with.
This is a man who is
already 88 years old by the time the War of the Ring ends, he becomes King of Gondor and marries Arwen. He then reigns for 122 years, dying at the age of 210. He is 20 when he first meets Arwen, 2690 years his senior, and falls in love with her; but it is when he is 49, after many adventures and experiences, including serving in Rohan and Gondor, that he meets Arwen again, she returns his love, and they become engaged, an engagement that lasts for 39 years.
The reason behind this is that he is the heir of Elendil the Tall, of the line of Elros, of mixed human, elvish, and divine (through Melian the Maia) ancestry, being very long lived. Also, he has been fostered by an Elf, Elrond, as Túrin was by Thingol. The love between him and Arwen can certainly be justified by the love song title 'No Ordinary Love';
because she, as an Elf, would (and does) in order to be his wife need to become mortal, a sacrifice that can be barely imagined.
What I'm saying here is that it is difficult even for fans like ourselves to get to grips with who Aragorn is, who Arwen is, and the nature of their love. Aragorn, while he does express doubt about his ability as leader in the book, has already had many years to deal with a lot of earlier self-doubt.