I am already feeling myself reach the end of one of these cycles where I am digging through netlabels and indie internet radio stations looking for the next niche subgenre to become addicted to.
Perhaps there is, if you pardon the expression, a spectrum of receptiveness.
I'm thinking there's something to your speculation, though.
If you purposefully go out and listen to new music, you'll quickly get accustom to the sounds of new genres. On the other hand, people who are not in the habit of trying new things never train their brain to enjoy new types of music.
Kind of the same feeling where you upgrade to two monitors and if you have to use a workstation with one just isn't the same.
On the other hand, I really appreciate the minimalism of some modern ambient scores, but I'm not sure me from 15-20 years ago would have had any tolerance of it.
Like you, I can't stand the music I grew up with all that much (maybe a few songs here and there), but I went through the trance/electronic fixation in the 2000s. Now it's almost anything that I enjoy, which probably doesn't say much, but I'm presently listening to some chillstep and was listening to metal covers of the sea shanties "Santiana" and "Roll the Old Chariot Along." A few weeks ago, I was listening to Norse-inspired works by Einar Selvik.
I can't imagine we're that statistically significant or if streaming may have some impact on availability and interest. I'm unwilling to believe it's a personality trait, for instance. (For another data point, I was born in the early 80s.)