Democrats aren't a left wing party, nor are they the party of the people. We don't have a left wing party in the US, we have no party that represents the people.
The Democrats represent rich corporate interests while pretending (poorly) to be an opposition party to the Republicans. Voters and rich donors have mutually exclusive interests, thus the Democrats have to pretend to support the peoples interests, but only until they get into office.
Any legislation that helps the people comes with strings attached, expiration dates, and/or are easily overturned, as it was intended.