I would argue that all of those descriptors apply equally well to Trump. I will hold off diagnosing either Biden or Trump with dementia as I am not their doctor. I will say, though, that both seem to be showing at least some mental decline, which is to be expected giving the advanced ages of both men.
The way I see it, Trump's inadequacies make it so he does not deserve a second term, but that does not mean that it warrants a vote for Biden. Biden still has a few months to lose my vote. In a sense, the 2020 election is a wash. Either we get four more years of what I would argue is failure under Trump, or we get four years of Biden. Either way, we are going to get a fresh round of candidates from both parties in 2024, and that is where my interest lies. With Clinton's loss in 2016, we saw the democrats take a nosedive to the far left, arguing that her loss demonstrated that a moderate could not win. The resounding rejection of Bernie and his ilk in the primaries against Biden seems to have tempered a lot of calls for more progressive policies within the democratic party. With Trump's win, we saw a rise in extremely far-right candidates, which seems to have been mirrored on the democrat side, leading to even greater political polarization. I do not want a far right candidate any more than I want a far left candidate. If anything, I would hope that a Trump defeat or a Biden victory would motivate more centrist or even independent candidates to run in 2024.