you got it backwards. ntr requires more plot than non-ntr. you need one more character for cheating to occur.
for real ntr you need to create the humiliation fetish. if this is missing, you might have such netorase as here. or things that are not actually ntr, but called so by people hating ntr and that other stuff, so they call that other stuff by the worst term they know, which is ntr.
but plot complexity is not the deciding factor. sloppy developers create for a perceived audience. creating for mainstream smut audience means competing with mainstream smut. and ai is not good for that. creating for nieche smut audience means an audience that has less games to chose from and even mediocre ai games can shine there.