There is no reason to believe that harsh prison systems are representative of the will of the people. In the 1990s, three strikes laws in California were enacted by public referendum. The margin was 3-1. 75% of people voted to put people in prison for life for three felonies--and they didn't even have to be violent felonies. And it was one of the most liberal states in the country!
Its political, and at least in the US, it traces its roots back to corruption and how unrepresentative the US government is of its citizens.
If you want to fix almost all societal problems, you first need a system of government that fears and respects its people. I don't care which permutation of state you pick, but if you want a government to care what you say, it has to care about its people.
Most countries have that problem. Its less overbearing because most European states have better implementations of near the same parliamentary system, but even those governments are often too centralized and too easily corrupted, and that breeds an unrepresentative state.
Making a government that acts in the will of its people is absolutely step one to fixing the problems it causes. Then you just need to persuade the people and thus the representatives to change it.