If elected, Biden will dodder around for a few months or perhaps a year or two as President in name while Kamala is de facto President. Then his dementia will become so blatant that he'll be forced out of office and Kamala will become the official President. So you're right, this election isn't Trump vs. Biden, it's Trump vs. Harris.
20 or 30 years ago, Biden would have made a lousy President, but one I could live with - a lower IQ version of Bill Clinton who occasionally said something sensible or at least pretended to agree with Republicans on some issues. Today, he's not only drifted far to the Left, but in his diminished state he won't even be calling the shots - the hate-filled, radically anti-white, anti-male Kamala will be.