Until now, I didn't realize that genetics and initial physical image was such a huge deal for some Simmers. To be totally honest, I don't understand the purpose or the goal of having Sims with 'perfect genetics'. I see that as being a personal thing individual to the Simmer desiring it.
For myself, I will immediately change a Sims looks if it has been shown to cause interference with their lives, after all the Sims is a social game. Sims such as Arlo Bunch, while not attractive to my eyes, have no problems socializing and building relationships in my game so there is no need for me to alter him. However, teenage Sims like Celeste GilsCarbo (Barnacle Bay) life was severely limited in part due to her looks. She had no friends, no skills except for a single point in guitar, her mother abandoned her which created hard feelings towards her family. Her step-brother thought she made an excellent romantic 'practice' partner in private but would belittle her in public. On top of that, she was working at the day Spa to pay the bills all the while failing at school.
Celeste is the only Sim I have ever almost totally remodeled because of those conditions. Her life is now a complete 180 from where she started. My goal wasn't to make her a raving beauty, just give her a better chance of being socially acceptable so she could grow.