*shrugs*
The best thing I can tell you is that 2020 was a winning campaign, and 2016 was a losing campaign. Biden hasn't been able to run a 2020 campaign because his credibility on "stopping the fascism, reigning in the police, stopping the forever wars, getting Trump" which was the core of his last campaign - is pretty much shot.
I have no idea if Harris is willing to admit that and say "we're doing what Joe promised but unlike him, I will deliver." She has to admit he didn't get it done.