Street photography is never perfect. Sometimes if we come back with 70% to 80% of what we were after it can still be a success.
I agree success is measure in many ways. To some, success is getting out and taking a few pictures and to others it's selling a great print for a lot of money.
But as to your percentage ratios, we also have to remember that different genres of photography have different parameters and challenges. As a studio portrait photographer, facial expression is a major concern, as is composition and making the subject look good. The impact, or love of the subject matter is built in. It's a family or a child and the buyer already loves the subject.
Street photography and photojournalism are totally different. They can hit a higher level on the appreciation scale but are harder to achieve. Getting all the elements right is far harder and luck and skill play a significant balancing role. And composition is essential.
Landscapes look easy but they too have difficult parameters to reach greatness. Composition is probably the main one and this is the area as well that great printmaking is probably more essential. Look at the raw neg of Moonlight over Hernendez. That print could have been boring without a great printmaker.
So all the genres have different challenges.
In fact landscapes may actually have the hardest challenge to be considered great since impact and emotional communication to the viewer is probably the most difficult.