Legends of the fall, Isabelle two

Just watched this movie for the first time last night. Really good, but so sad. Something that I feel was a big flaw in the story is Tristan and Isabelle. Mainly because the character of Isabelle is never really explored and shes mainly a character on the periphery that I never got to know or care much about. For a character as compelling as Tristan, I would have liked to invest some emotional connection to his wife and this movie didn't do a good job of that. We see them together happy and in love, but it feels just sad because I don't care about her, there's no joy in seeing them together. Am I the only one who feels this way?