When you do something the same for 15-20 years, it makes you start to feel like its getting repetative and you might (and it does seem like many of these studios do) just start to push them out quickly with less effort as you did in the past. I haven't heard any of these character albums starting with Gatekeepers on that have sounded original or 'good'. Just like I described, the same background beats and synthed effects, but with a different singer and repeated effects mixed in.
In fact, its getting quite embarrasing listening to them. It was cute listening to a few of them WAY back when, but now its just....the charm wore off and now its like they're forcing the cute on and its creepy. All I can see is the actual picture of some 32 year old Seiyuu dancing around a recording studio pretending to be a 15 year old anime character and trying to sing.