Progressive Politics

The parties I voted for in the last 5 elections where all center left.

Part of the problem with American politics is that you've got a set of centrist policies (fund public education and health care, regulate hazardous businesses, guarantee some degree of public safety, high speed mass transit, business friendly borders) that are significantly different from actual policy that the Congressional consensus reaches (privatization of education and health care, business deregulation, privatization of security, mass transit neglect, borders that are hostile to trade and travel for anyone who isn't a corporate entity).

A system where multiple parties have to form a coalition gives you the voter many options.

I haven't seen that bare out in the European block. Christian Democrats dominated German politics for decades, despite a multi-party system. The Netanyahu government has built coalitions that lean further and further to the right, until he's embraced outright fascism to stay in power. Taiwanese parliamentarians openly brawl on the assembly floor, without ever shifting domestic policy in a popular direction. The UK political landscape does not appear to meaingfully improve with the introduction of Scottish Nationals or Liberal Democrats.

You might have more options on paper, but the real policies always seem to favor private corporations and international arms dealers, regardless of which faction or coalition composition wins out.