Earlier quoted context omitted.
To a chronically obese person: Just stop eating. To a person in poverty: Just save up money and find a job.
It seems to me that the real problem is that these issues have root causes which really need to be addressed, and that's why telling the chronically obese people "just stop eating" doesn't work, because it isn't addressing the root cause. The problem, however, is that addressing the root cause is extremely difficult, or even impossible (for those trying to give advice), so people don't know what else to say. For the…
I don't know, but if one can't think of anything better, then I think it's better to shut up, or just acknowledge the problem and be supportive but refrain from offering unwanted non-solutions that implicitly blame the victim and trivialize their problem (you aren't "just doing X" therefore it's on you) and simultaneously frustrate/anger/depress them because "just do X" is impossible (or not a solution to their problem).