Understanding poverty starts with empathy. People thinking that "poor is a mindset" are lacking in that. It's not that simple! You can't just mind your way out of poverty! This isn't a math problem.
Too many people buy the American dream of "If you just work hard enough, you'll be successful.". If you believe this, then you'd have to believe the opposite: "If you're poor and unsucessful, that means you didn't work hard enough, you must be lazy.". And too many trust-fund kids or kids from rich parents who could afford to send them to expensive schools (or rich enough to live in a district with a well-funded schoo…
My siblings have a similar complaint when my Dad essentially implies that they were lucky in having the successes they have had. They do still somewhat understand what he means, but they dislike it because they think he's dismissing the hard work they put in. Of course, they don't see that he applies the same to those experiencing extreme poverty.