EXACTLY! As a professional DNA girl (it's my job), y'all are giving genetics more credit than you should... Sure genetics have to do with texture, strength, thickness, etc, but most of us (exception with alopcia, and other genetic disorders) have the genetic make up to have long hair! It's what we do to it that prevents it from maintaining length or growing faster.
Leaving it alone is the way to go! Every one of my friends with long hair don't prescribe to the methods described on these boards. They really just leave their hair alone. My step mom has always had BSL- midback length hair, and just got her first relaxer about 2-3 years ago. Before that she was press and curl and did few shampoos because she wanted her press to last longer. It's no secret that low manipulation will help you retain hair. My hair actually got worse when I first came to LHCF because I was trying to do all the CW, daily washes, etc. I found it was too much for me and I have thick, coarse hair. Go figure.
I say stick with what works for you... If genetics were the only key, then many more of us (AA women) would and should have long hair. JMO.