Biden believes that if a Democratic President begins working towards bipartisanship, Republicans will have an 'epiphany' and follow suit.
However, the reality is that the Republican party have showed themselves to be stubborn and uncompromising, and have no incentive to work with Democrats.
While early in Joe's career partisanship was common, this is no longer the case - party politics have changed. Additionally, Biden's early 'compromise' involved cooperating with segregationists.
The bipartisanship of the Obama era was not a success. After Democrats lost the House and had a progressively decreasing proportion of the Senate, in reality bipartisan initiatives largely failed.
A future Democratic nominee needs to be able to hold fast to their policies and introduce large-scale change through policies like Medicare for All and the Green New Deal, rather than working in a bipartisan fashion and only implementing watered down versions of policies for huge concessions to Republicans.