This is a relevent comparison, for example -OZ- and DEATHGAZE were both pretty popular bands at one point, but they stuck to the same routine. To continue to grow people need change and they need to take risks, and I think the problem with this album is that not enough risks were taken, and you can only do the same thing so many times before all the tracks start to blend together and don't have anything special because if we haven't heard it before, we've certainly heard something with the same energy and direction from whatever artist is at hand. So I agree with Zess.
This isn't meant to be offensive, but while all of those bands have/are currently successful, personally speaking Their recent releases don't phase me either since they tend to keep the same pattern. SID has had a strong following for a long time, so that's just that. Mejibray is popular for more reasons than their music, to be fair. As for NoGod, Matenrou Opera, and D... I'm amazed that they're still around. I don't mean that in a "wow they suck" way, but their releases HAVE indeed become repetitive and don't really offer anything new.
All I can say is that... by being a musician, and to be a successful one you HAVE to take risks. Yes you'll lose fans if you try something new, but you'll attract much more by presenting something that wasn't offered before. I hope that Arlequin is able to grow and try new things with their music with out losing their own individual sound. That's why they sparked attention in their past releases, because they sounded like their own. While their sound does mirror certain genres, they were still their own and there was something that set them apart and made them stand out. If they want to stay right where they are at, sure keep releasing the same formula over and over again but even then people will get bored and put them on the back burner. If they want to grow, they need to go head on and take a few leaps every now and then.
Off-topic: SID mentioned going pop a long long time ago. I think they somehow fit that, however they do seem to keep some VK tendencies. I wouldn't consider them Oshare kei either.