The link between drug use and poverty is far from clear. While there is a correlation between drug addiction and poverty, there has not been a causal relationship shown between the two. In many cases, poverty may be a result of drug addiction rather than a cause. Consider the much talked about opioid epidemic, for example. The people getting these prescriptions tend towards middle rather than lower class. When the pill supply runs out, either because they can’t afford them anymore or can’t find a doctor to prescribe them, they turn to much cheaper and readily available street drugs like heroin, and at that point they’re more or less locked into a downward spiral into poverty.
All of this is to say that if we were to somehow “solve poverty” (even putting aside the vast oversimplification made by such a statement), while it might reduce rates of drug addiction, it by no means would be an overall solution to the problem. Addiction respects no socioeconomic boundaries.
The link between drug use and poverty is not relevant. It's only addiction and unhealthy drug use that are problematic. Alcohol being the number 1 problematic drug by far.
You jumped through a lot of hoops to explain that there is an avenue from middle class to poverty through drugs, but any avenue from drug use to poverty pales in comparison to the avenues from poverty to drug addiction. People who have no place in society, because they have nothing worth contributing, or for whatever other reason they end up in poverty, they find good feelings and usefulness in drugs, in the participation with others in a similar position.
The link between poverty and drug use is very very clear.
All of this is to say that if we were to somehow “solve poverty” (even putting aside the vast oversimplification made by such a statement), while it might reduce rates of drug addiction, it by no means would be an overall solution to the problem. Addiction respects no socioeconomic boundaries.