Personally I don't have to confess anything. From an academic point of view there are some big holes in pre bop era, vocal music and in the free jazz avantgarde of late sixties/early seventies. Years ago I decided I had to explore the land outside my preferred music, so I bought some of the 'essential' set like RCA Ellington, Hot Sive and Seven, Mosaic like Django and Bix, ecc. I don't listen to them very often, nor I acquired a better view of History of Jazz. I would say that the only set I regularly listen to is Billie Holyday. Anyway I like a lot of music after the 60's: Jarrett, Zorn, the electric Miles, ecc.
It's the same for classical music, I can't dig most of pre Mozart music, and of Mozart I prefer his late works. Mahler and Bruckner are the other time border, after that I appreciate few things. I don't like Opera, a part Rossini and Mozart.
I don't feel guilty about it. I am a music lover, not a teacher, producer, musician, critic, ecc..
You can put it in this way: An alcohlic is different from sommelier.
BTW I have some Organissimo records.