Democrats’ only real incentive is to be better than Republicans.

I disagree with that...their only incentive these days is to NOT be Republicans. They've taken up traditional right leaning republican policy at this point and are getting away with it. For example: The ACA is terrible, we NEED universal healthcare, however, the D's are content letting big health insurance continue to rape the US. The D's have also strongly backed off climate protections, and honestly, it's too late for climate change so that's maybe moot.

The point is, they don't have any incentive to actually push policy...they just need to point and say "Republicans are bad" and the donations roll in.