What do you think of this statement?

I saw this on posters displayed throughout a middle school: ability = determination + attitude. It sounds so absolutely stupid to me because there are other factors not even considered especially physical condition. Think about it; would you say a blind person couldn't see because he didn't have the right attitude? Of course not, no one would. So a state medical condition like paralysis or blindness should also be considered. What if the condition weren't as obvious, let's just say the person had an allergy celiac disease, which hard to diagnose, and can affect someones mental state directly or indirectly by low blood count. Low blood count means less oxygen and therefore lower ability. The point is by making all ability just a matter of attitude and determination you leave a lot of people with subtle medical and psychological conditions open to hatred, people who don't deserve blame. Have you ever been the victim of this kind of mentality?