I certainly agree with you but you are discussing this in a much broader context.
Situation 1 : A person does not seem to be getting along with his wife of several years. Plan A is to figure out what they can do to save the marriage an alternate plan B is divorce. Unless the situation is really extreme, plan b is certainly not applicable in this context.
Situation 2 : An intelligent, compassionate and a caring individual aspires to become a doctor someday. Unfortunately he is poor in mathematics. This cause him to get less than stellar grades in math related subjects like chemistry & physics. In this situation, plan A is trying to figure out what they can do to improve the situation. Plan B, which most people would recommend would be " Dude, perhaps you aren't meant to become a doctor". Look for plan B. I have witnessed this on a few occasions.
Now in a different context : An individual who does not have the attitude or the aptitude decides to pursue medicine, due to parental pressure or the aspirations of harnessing a large fortune and becoming a millionaire. In this case, a plan B would be an appropriate suggestion.
Most of us use alternate plan in our daily lives. Right from choosing an alternate path on the roads to reach our destination on time. Approaching a problem from an alternate perspective to even using this strategy when buying groceries ( need to buy almonds for a recipe but the store does not have it, second option would be buying walnuts or pecans instead of driving far to get almonds ). In a professional setting being flexible, open to alternative ideas is an absolutely important trait. I certainly get that.
Unfortunately, on several occasions, I have seen this idea of an alternate plan becoming a hindrance rather than a help, especially in a context such as OP's situation. It prevents you from going that extra mile which separates the winners from the losers and which makes things perceived as unattainable to be attainable.