Never understood "fluff" in light novels. Just doesn't make sense to me. Setting that aside though, it's still pretty terrible. Story doesn't even try to pretend that the MC isn't a Gary Stu. Everybody instantly loves him, and he gets everything he wants. All the characters can't even be called cardboard cutouts, and the girls even more so. There's no difference between any of the girls, and they're essentially treated a objects to fawn over the MC. The writing is so simple that I swear, even a child would find it boring.
I will admit though, I laughed when he instantly defeated the all powerful evil demon lord. That was funny, shame the rest couldn't be more like that.