Because they don’t win due to neoliberalism, they win due to their opponent being the literal antichrist. The point is to force Republicans to change their (supposedly) losing strategy, and have Dems react to that.
You can see how, for example, after the three consecutive Republican terms of ‘80-‘92, Democratic candidates have shifted more towards the right on average, in order to recapture more “average” voters.
I don’t have the competence to lay down accurately the process or know the best examples for it, but it’s pretty much basic game theory. If you keep losing consensus you have to adjust your strategy to be more similar to whoever is winning.