Quinn would be one-sided self-centered bitch, if there was no romance possibility between MC and her. If you start getting closer to her, then her character becomes also very interesting and conflicting. Maya and Josy were a bit of a one trick pony - they had one big secret, but since that has been revealed, they didn't develop anywhere, nor did they do anything, also our romance with them is extremely vanilla, no difficulties, no conflicts whatsoever. Jill as a character is pretty simple, however our romance with her is the most difficult and interesting. Sage is a bit of everything, dumb and clever at the same time, her path is also the easiest, it is almost more difficult not to bang her constantly than to do it.
I also have nothing against simple characters if they are well written. For example Riona is pretty simple character, but everything about her just fits the picture, she is a great character. Maya is also very well created even though many ppl don't like her - she being a movie watching feminist kinda feels real, or Jill, the sensitive virgin rich girl.
To me Sage doesn't quite work as being really clever to research but at the same time also dumb not to see Chad or Quinn. But then she is emotionally intelligent enough to try to help Maya. So she is clever and sensitive adopted girl but also a big tit slut who is leading all the girls who are prostitutes behind her back, and also she is a sex freak but doesn't realise her bf is gay. But nevertheless she is very likeable just sayin' that maybe DPC wrote a bit too much into her.
Bella also has two strong opposite treats but with her it's more believable, you can see that see is a suppressed party/sex queen who simply probably chose a wrong marriage.