She was
never gorgeous or even cute IMO, but, I doubt it was about her looks. If Michael wanted a beautiful woman, he would have gotten one. I think their relationship seemed to be more about proximity and trust -- they seemed to be more like friends that made an agreement because he wanted to have children. He had been through so much at that point and he trusted Debbie. I can really respect the fact that Debbie has never come out to the media to air dirty laundry or try to make a quick buck or have her 15 minutes.
Anyway, it's nice that Paris seems to be building a relationship with her.
And biracial children can look like a mixture, completely one race or another so no, Paris is not "too light" to be the child of a Black man.

Mariah's father is Black as well -- genetics are unpredictable.