There is a lack of adequate textures and lighting, as all the metallic material shines unrecognizably bright, as opposed to how these maps usually look. Some users have ported these same maps, with much better results, so I don't believe it as merely a "Use mat_specular" problem, although it really disguises itself well as one.
I would recommend the creator of this pack to go to the J2 discord, or contact users like Panch, who have dealt with porting NIPPER maps before.
There are maps missing, like de_absurdity.
However, this is all the criticism I have. I actually appreciate the fact the songs are left in these maps again.
I really hope that my input helps in some way.