I see what you mean. I started liking Ayu's music because it sounded good. I don't understand the music, since I don't understand Japanese (well, I understand a
small bit- not enough for the songs though). But luckily for Ayu, her good lyrics match her good songs.
But what you said about Greatful days is true. Although not for me, because I liked it before the other & songs. True, some people didn't like it.