OK, before I go on, this is not an attack on anyones personal taste, so calm down if my silly words rile you up in any way... this is a thread about those 'classic' acts that you can't get to grips with, no matter how hard you try...
For me, it's gotta be Bob Dylan. I just don't get it. I like some stuff (Blood On The Tracks is a pretty good album and some of his 60's stuff was pretty decent) but most of it just sounds like someone's whose been allowed to get away with his mumblings for far too long, as if a strong producer should have tapped him on the head and said 'um, where are the SONGS?'
I'll go for Lou Reed as well, and I'll include The Velvet Underground in this. All hail Lou! Er, what was the last decent song he wrote?

And, yes, I'm going to throw Mr Lennon into this. Respect for the amazing stuff he did with The Beatles and one of the greatest voices ever heard on this silly little planet... but when he threw his lot in with Yoko, wow, that shit made 'Revolution 9' sound like a pretty pop tune. At least Mr McCartney made music that anyone wanted to listen to! For the record, not a fan of old Paul (I personally thought George was my favourite Beatle), but there are few of his tunes that I'm quite fond of...
OK, there it is, please appreciate that this is a PERSONAL view... what other 'classic' acts are not all that fond of... C'mon, be brave!