Music prior to 1994 may have had its share of junk, but at least it was junk that was trying to talk about something. Today you have things like Justin Bieber and One Direction, as well as their female counterparts, that all spew out trite garbage that means nothing because it was never meant to. The people writing the lyrics to this crap don't care about music, they care about making money and know that they have a vehicle to do so very successfully.
The only thing I'll say is, Soundgarden, Alice In Chains, STP, Metallica, Iron Maiden, Dave Grohl, Red Hot Chili Peppers, The Offspring, The White Stripes and hell, even Radiohead kept making music after the 90s. So, I mean, there's good music before and after 1994, and also bad music before and after.
In my opinion music is really not something that people may agree on in terms of what is better than what. It really depends on the individual in many cases in terms of what they like better. So I don't think saying that post 1994 music is any worse that pre 1994 music.