Something those on the "resign" side should consider: No President runs the country by themselves, nor do they make decisions in a vacuum. They have advisors and Secretaries, all of whom have hundreds of supporters. The President, more often than not, merely chooses what he thinks are the best offerings of this large team.
Now, it is clear that Biden has surrounded himself with a very competent team -- his record in office shows that (only for those who will actually look at the record, instead of what Fox says it is). What did we see of those Trump surrounded himself with, especially in his last days (but even in the early days, when he was appointing and unappointing people at warp speed)? And who do we think he will surround himself with if he wins? Clever, independent thinkers, or toady's who will swear to do his bidding?
Biden should not resign.
I agree that Biden's team would do a good job in a second term.
But the problem is that the public perception is what counts in terms of getting him re-elected.