Encumbant advantage? In this economic climate, it's exactly the opposite. People who are feeling increasingly fed up with a world in which they cannot make ends meet vote against the status quo.
4 years of Trump got people to vote against Trump. 4 years of Biden got people to vote against his VP.
Biden himself would lost even harder than Kamala did.
I'm basing my analysis on the observable trend that incumbents lose when the economy is poor. As well as, y'know, Biden's abysmal poll numbers after the debate, the reason he dropped out in the first place.
You're the one who started insisting incumbent advantage would've been a thing here, where's your crystal ball?