Bring them further left how? Why would they need to do anything when you'd vote for them anyways? Every election both parties move a little bit to the right, and you have no choice but vote Dem. What can you realistically do when the only power you have is voting unless you are a billionaire? Your electoral system is truly fucked and the probably of it fixing itself is low, because why would the party in power want to change the system that just gave them that power?

All I can say is leave if you are able to.