I think the biggest problem is that Ayu seems to be very comfortable right now. She's the richest Japanese artist, the best-selling female solo artist of all time, and is already a legend in the industry. Sometimes I feel like she's very aware of that and that's why she doesn't feel the need to create anything new.
All of her recent released have been rushed, songs being written and recorded in only a couple days, all of her videos being single-shot (this is not an aesthetic decision anymore, it's just lazy). Every single song sounds like something she could have done at any time in her career, every single picture simply shows "Ayumi Hamasaki being pretty in a cute dress while standing in front of a pastel-coloured background."
I miss when her albums used to deliver a message, or at least show a new side of her. I know it's impossible to always inovate, but everything she does nowadays is just
too safe. Nothing changes, absolutely nothing. It saddens me to say that her last "unique" release was Party Queen. I hated the album but I appreciate the album lyric-wise and the attempt to try new genres. She complained her entire life for being "a product," but now that she apparently can be herself... it's just not interesting.