I'd like to think it's just a personal thing.
For instance I'm not sure how long ago you mean by the music of 'yesteryear' Aggers, but suspect you mean your own youth.
My youth would cover from eg the Beatles, Rolling Stones, 60s/70s/80s, but I certainly didn't like
all of the music that was around during that time. I had quite eclectic taste from a young age, enjoyed my mum's EPs and LPs of the musicals, her Glenn Miller - but not Acker Bilk - but then she also had Elvis, Billy Fury, etc, which I loved too.
But the Beatles were in the charts 50 years ago, which can hardly be called modern!
Now, whilst I still enjoy a lot of those older records/artists, a lot now sounds terribly old-fashioned and dated (Dave Clark 5 anyone?) I also like an awful lot of much newer stuff.
The local radio has a daily 'golden hour', one year from the last 40-50 years, they play the records that were in the charts for that year. People are on the phone every day, getting excited about guessing which year, and all the time saying that was the best music, that was the best year of their lives, etc...and I just don't get it
I'm not nostalgic in any way, would hate to be stuck in some idealised version of the past, and have always rather hoped/thought there are bound to be even better times to come