Coldplay - The same songs over and over again, did the lead singer get married and have a kid already. Why the hell is he still whining about love?
Mariah Carey - The problem with her is she used to be a singer. She now relies ons skank tactics and her music is indecernable to the hundreds of similar and like artists out there.
Justin Timberlake - Just an image, he sells music by looking cute and trying hard to be sexy. He's moved on to movies where once again, his image is all there is. He is a hologram with no substance to him.
Lady Gaga - Her music started out fine but then she started using shock tactics to sell her music. The "meatsuit", your music is empty when you have to pull stunts like this to get it to sell, the whole egg thing was silly too.
Justin Bieber - I don't get the appeal. The voice is grating with the same song over and over. Not to mention collaborations with desperate performers looking to ride the gravy train to fame.
Maroon 5 - They started out fine I guess but they are everywhere and annoying. I dislike that Moves Like Jagger song. Adam Levine is gross looking too, "drug junkie chic isn't sexy". Not to mention the endless PR to sell this guy as a sex image... eww!
Nickelback - Everytime I see or hear their music, I cringe. That guy sings in the same voice every time, can you imagine calling him up on the phone and he sounded like that.
Modern Rap - Old school rap used to be about positive messages, then it got tainted and split apart to many variations. Most of it is bitching about being the downtrodden, the other end of the spectrum is those rappers boasting about how legit and criminal they really are, when infact they are or in most cases, not. The music tends to be annoying and often heavily borrowed from other places. Lame... that's not talent, that's called lazy. I dislike eminem not just because of the gay crap or the women issues, but in general his music provides means of preaching intolerance and stupidity.
Modern Country Music - The music is crap, its not even country anymore, its some weird amalgam of pop, rock, rap, etc. It sounds ridiculous, I dislike Shania Twain for this.
I think music in general has pretty much hit a brick wall, everything that could be said about love, hate, heartbreak, freedom, oppression, unity, etc has already been said. Its just dressed up differently for the party everytime we hear it.
I like listening to orchestral or instrumental music, because it can mean or be anything you want it to be. The interpretation is yours and yours alone. Sure, modern music has that too. The above performers I have mentioned lack the quality of humility. This is of course all just my opinion on the matter.