It usually comes down to two democrats running in the primary .
A lot of money is invested in some IL republican wealthy suburb areas where they always win .A Dem might run but will most likely lose.
If rich iindependants or republicans were going to swing dem IMO it's not for a LW socialist but maybe a moderate dem opposing a crazy repub tea partier but now maybe part of the current dem party will stay home on moderates.

So one type of candidate or a single solution for the whole country is not something I can imagine
It's a big country with lots of local flavors

Areas do change demographics though . Arizona Nevada are examples and that is where I hope the party concentrates , on the changing demographics where there is serious chance to win and change.
Putting money on wild cards is a big gamble unless the suggestion is they do not need funding or a ground campaign and will win anyway because they speak to the people
If they point to trump did it that way, then they may also have to be ready to self fund, play his tricks and also get involved with voter supression etc realistically to gain ground in some of those red areas IMO