Your analogy doesn't work at all.

The answer you're being asked for needs to be a solution (what can replace capitalism?). The answer in your analogy is an observation (the plane crashed).

It's fine to not have answers, but then your position is pretty useless. A societal system is a mandatory component of our lives. You can't get rid of it without it being replaced with something else. If we don't replace it, then one will arise naturally.

To follow your cancer example, it's like a cancer patient saying they don't want chemo or radiation because it's not good enough. When they are asked what they want to do instead they just say "I don't have answers, I just know these treatments aren't very good".

Winston Churchill is quoted saying

Democracy is the worst form of government, except for all those others that have been tried.

Pretty much the same applies to capitalism.