It's kinda harsh to say that way. Actually, it doesn't always apply like that. There are many poor people that're smart, innovative, and have great ideas. But they're trapped in a hard situation for them to fully express themselves and struggle for what they want.
There are many rich people that're fool too though, sometimes they're rich because of luck, not hard work. So you better not generalize people like that, because we can't really know someone's fate, rich or poor. And also, everyone can be stupid. Maybe a little, maybe too much that really annoys us.
Absolutely! Our standard of living now does not define of what our future will be. We are strengthened by our bad experiences, wrong decisions in the past, while keeping our strong determination. Stupidity is about having no respect of what you earned and is abusive with finances or expenses. Whether you're rich or poor, it's very important that you have self-discipline, are responsible, and value-oriented.
What causes poverty are due to lack of control, corruption, over population, greediness, and a lot more. If we are aware of all these things, we must find ways to survive. These should not be the reason to give up and be careless. We all have the potential, let's make use of our time to be productive.