^ well I think she isn't 100% irrelevant to the public of course, like what you said Days for example was her recent hit that resonated well with the general public.
However, when you think about it... why did Kana Nishino's album sell over 600k? How did ABK48 & ARASHI sell like hotcakes?
Isn't it because they're relevant to the public in whatever ways; music, personality, style, etc that almost made it compelling for people to buy their stuff?
For Ayu's case.. she definitely had such a relevance back then from 2000-2002 I guess, but I had a feeling she started to slide from 2004, where she made the OMG statement about quitting avex if Max was gonna be fired.
THAT, to me, seemed like almost a scandal to the public, like "omg how could a woman make such a powerful statement!? it's not right!"... like what you love to say, Japan likes it when their female idol has no brains
so i think it was around that time where people feel that "ayumi hamasaki" isn't relevant to the public; like she couldn't represent the women well, for example.