That does seem to happen to some people, ok a lot of people, as they hit late middle age ie they start liking bland music. Although one person's bland is probably another person's amazing to use one of the most overused words in the English language.
Purely personal joint view from within our two person household (me nearly 64 and she 57) is that there are three things that define the late middle aged onwards:
1) a sudden interest in motorhomes,
2) the wearing of beige and brown clothes by men (along with blazers, sports jackets and slacks), frumpy floral dresses and bright coloured 'cagoules' (along with pearl necklaces and pearl drop earrings) by women,
3) listening to humdrum music by the likes of Sir Tom, Val Doonican, that Buble fellow and other assorted crooners. Usually accompanied by 'in car' collections such as 'Road Trips', '60's, 70's or 80's Classics, 'Motown Greats' and other assorted banal curations. Favourite radio station being the dross that is Radio 2 or Local Radio whose major headlines involve cats, grandchildren or strange shaped vegetables.
A bit TIC but that's how it seems at times.