I am happy if you are happy.
I reckon Mark Rippetoe would be what I would call an "external stressor control". In my training "environment" i.e. a shed without a trainer or coach present my outcomes may be somewhat limited compared with say training with Mark at his Gym. He would I am sure push me further, however I have to motivate myself, this is a limitation but we make do under the circumstances.
As to genetics, well I am not really suitable for weight training, I don't weigh enough, I am too old etc, etc, this is also a limitation, however this does not stop me from having a go. What I do have is motivation and that is where the difference lies. And the bonus is I get to be a big head? Ha!
I am happy if you are happy.