@zacharius
I don't think it's a natural process of aging because music appreciation and skill can grow over time at any age. There are 80 year old musicians who have grown musically all their life and are demonstrably better than their younger selves. Presumably they are still moved by music.
However, as I notice more things, and pattern match better, my tastes change, and I get bored faster, and I have to seek out different inputs. Same with reading books.