On the first two paragraphs we're agreed.
Trump doesn't have all his marbles either. He slurs his words and confuses simple facts. I don't think mental capacity is a differentiating factor between him and Joe.
I don't go home and cry at night that Donald Trump said mean things to me and hurt my feelings. On the other hand, when he mocks disabled reporters, POWS, and fallen soldiers, calls for the Constitution to be "terminated," and cozies up to autocrats, I'll take him at his word that what he's saying is a reflection of what he believes. You're ok with someone with that attitude representing the "free world?" He doesn't have a problem with the unfree world; he openly admires its leaders.
I have a few Chinese friends that speak a lot about Xi and the grip he has there. They've said that it was understood that Xi was going to be a strongman, but people were more or less ok with it given how the economy was doing. Now their economy is in the shit, and he's transformed the entire country into a cult of personality centered around him. It's too late for anyone to speak up, and if you spoke up earlier, your concerns were dismissed. I see too many parallels here of people shrugging off Trump's aspirations out of some vague appeal to the economy.