I agree with you on this, and I'd wager most politicians do, too, but when you have new young politicans like Alexandria Ocasio-Cortez becoming the face of the party it doesn't help. She's so far left she makes Bernie Sanders look like Sean Hannity. My guess is that after she has officially taken office more experienced members will pull her aside and coach her.
I don't think the party is as far to the left as it seems, but all the attention is on the few who are. They have a bit of an image problem that doesn't help their cause.