Because they rely too much on a "youth culture" gimmick. We haven't seen a group rely so heavy on this since GFriend and we all know how that turned out.
So far NJ is trying too hard to show everyone how young and fresh and care free they are while not realizing that they won't be any of those things in a few years. Again looking at GFriend shows they began to decline when they tried girl crush.
One could argue the difference between these two groups was GFriend was targeted towards males while NJ is targeted towards females and males dropped GFriend because they "grew up" and NJ audience wont do that.
But Twice has survived for so long cause they have mastered every concept. Same as SNSD did. And with NJ coming out the gate so hard with "this is us! its y2k baby" What's gonna happen 3 years from now when that is played out?
I guarantee Attention and Hype Boy will end up being a blessing and a curse for NJ cause they will spend their entire career chasing their own debut. Everyone here knows no matter what kind of success they have in future they will always be known as the Hype Boy group. Twice is not known as the Cheer Up group anymore.
Just something to think about before Baby Monster does to them what they did to IVE.