I think that Ayumi got progressively better from the time of her debut up until around Memorial address and MY STORY. Those are my favorite albums by her. (miss)understood, Secret and GUILTY were kind of the leveling out point for me because I love all those albums too, but I don't hold them in a higher regard than their predecessors. However, I would have to agree with the reviewer on the point that NEXT LEVEL really wasn't a good album. I think it's really one of her worst albums. I don't hate it... but I really just didn't like it. The singles were spectacular though.
And for me, yeah... Ayu has declined recently. I didn't like NEXT LEVEL and in my opinion, Sunrise / Sunset was lacking a lot. I've got pretty high hopes for You were.... / BALLAD though, so I'm not complaining!