At what point are you willing to concede that it might not be feasible for someone that isn't you? If it were 10% harder do you think you would have stuck through it? 50% harder? The numbers say the proportion of people who are successful is very small and there are sure a lot of people who are trying
Edit: I'll add that I've successfully shed 100lbs through discipline before. With the life I currently as caretaker for my son I don't nearly as much room in my life for the mental overhead that sort of change in diet required me in the past.
I can imagine it being a lot harder. There are all sorts of arrangements that either enable or reinforce the types/volume of food that you eat. Still, I think people should try to be aware of their own situation and try to identify those factors that promote weight gain. Even if it was harder, I still think it's inappropriate to say it's "basically impossible" and to deny common sense.