I will agree with the longstanding precedent of incumbent-advantage; but I do not see how that shores up support here and in the now. Put it this way: Polls show incumbent advantage is doing fundamentally nothing to put Biden past the numbers he needs in order to cross the finish-line.
And But don't you think Biden's numbers -- steadily declining for months if not years, mind you -- are sort of baked in? Media saturation has taken place, and Biden in the spotlight long enough that projections would suggest nothing will fundamentally change and that these are losing numbers -- yes? So between knowing we will likely lose versus taking the gamble of garnering viral excitement from nominating a younger fresh face, the latter would be better in my view.
Look I'm sorry, but you gave zero response to the damaging statistics I mentioned except to point vaguely toward incumbency which clearly isn't helping enough with the output of those statistics. So can changing candidates do more? I think so.