Their hearts and motivation are in the right place. They see pain and suffering in the world and truly wish to remedy that. Unfortunately they make the mistake of thinking that Government is somehow capable of creating a paradise if only a few more laws are passed. Conservatives recognize that mankind is a fallen creature and that government can function best by allowing maximum individual Liberty in which self interest at least can be used as a tool for good (see Adam Smith). Liberals pretend that government is somehow above self interest and corruption. They believe mankind is capable of perfection and that by replacing selfish moneyed capitalists with mythical selfless government bureaucrats they can right every wrong. It is a pipe dream, doomed to failure and disillusionment wherever it is taken to its logical conclusion in extreme socialism.
The world is a sad and brutal place. But politicians are sad and broken people just like capitalist fat cats or selfish conservatives. Mankind does not have a political problem. Mankind does not have an economic problem. Mankind has a sin problem and the best thing government can do is put up guardrails in the form of civil society and give us maximum individual Liberty to seek our own personal salvation and redemption