Of course he's too old. But his likely opponent is too everything else.
Biden painted himself into a corner by doing to Jim Cliburn what Keven McCarthy did to Donald Trump. To get the nomination, Biden had to promise to pick a running mate who, as everyone knew, could not run four years later. Sen. Harris was not presidential material, but Biden made her both his heiress apparent and the reason he had to run again, all because the Democrats are as much about identity politics as are the rednecks who vote for Trump.
Race has explained American politics since the founding. Until we all intermarry, and there are no visible differences among us, we will vote our skin color, and, eventually, become a failed state as a result. I mean, seriously. On what planet does aid to Ukraine depend on immigration policy? How can Sen. Romney, the least assholish of the Great Obstructionist Party, talk about a Ukraine-border "deal"? It's like a father threatening to kill his kid unless his wife lets him do you-know-what on his half-birthday.
How can one not be an authoritarian if this is what "democracy" looks like?