Has music really gotten worse, or are we just into nostalgia?

I hear a lot of people talking about how mediocre Justin Bieber, Kesha, and a lot of other current artists are compared to those of the previous generation, but I wonder if everyone is remembering the 90s correctly. When I was growing up there were a lot of good bands like Nirvana, but we also had very poor acts in the same decade. 98 Degrees, Mandy Moore, The Spice Girls. Do these ring a bell? I think a lot of people are just overcome by nostalgia, so they find these groups to be kind of endearing rather than annoying. There's going to be bad music in every generation, so I think we should just let it slide. What do you guys think?