The issue is not that leftists are not trying to solve problems. The issue is that they are not trying to solve material problems for other people. They are trying to solve the problem of meaning for themselves, and pretending to care about others in the process. Yet, if they cared about outcomes, they would weigh them against alternatives.
Communism was and is a disaster. Most of our social welfare programs today are bankrupt, and the War on Poverty did little but destroy the institution of marriage among those who needed it most.
Why are these facts not openly recognized, and well intentioned alternatives offered? Simple: solving problems was never a core consideration in the first place.