Let's be purists and kick all those "Reagan Democrats" out of the Party so their constituents can vote for them as Republicans and we can lose. You seem to think making your Party smaller will help win elections. The problem with that idea is that those more conservative Democrats represent real people who agree with their positions. Send them across the chamber and their supporters mostly go with them. The country is more centrist than you think.
I say don't kick anybody out, and do let the socialists, unions, and DSA in. The Democratic Party needs their input. If they can convince the more conservative members with the quality of their ideas and proposals, then the Party moves left.