IMO this work on the story side is pretty much how Takeda's NTR progression usually goes if you ever read anything by him (Ima Real, ManaTama, Ajisai for example): starting with vanilla, using "plot" to start the sexual harrassment, sexual training, the final switch that makes the heroine loses themselves. It's no big deal if you compare it to idk, some real good dramatic movies out there because obviously it still has plot holes in a hentai logic setting, but at least Takeda put effort into it to make the NTR less lazy.
The game even has events that explained why each character eventually loses level and how the girls slowly drop interest they had towards Kurt.
And yes, knowing how this is mostly a solo project Takeda is to blame because he spread his time for 3 projects at the same time. I wouldn't expect him to do a game that actually has gameplay because that's how it feels for most Japanese circles "making games". Just glorious nukige made in RPGMaker.