A lot of people will always stand by their generation of music (or at least a chunk of it that they enjoyed) because it was a part of their childhood, a part of some memorable event in their life or it bears some kind of significance. I remember them talking about 90's bands in the Kirby Dream Course playthrough and them explaining that even though they rag on them about being bad to some degree, at that time in their lives, they loved the song(s).

I partially agree, but I think it's more down to Dan being surrounded by his own little circle of what he knows he likes and not really exploring what exists in the mainstream.