I think more damage was done to Biden as his supporters thought the Republican narrative of doddery Joe was mostly fake, but he just went ahead and made their argument for them.
For myself, I think he has a strong record that is based upon his long experience, but I don't see age working for him going foward. He can retire with pride intact and put his name behind a turn-the-page to a fresh generation centrist candidate.
I'd support a cabbage over Trump. But he was the man we know. No surprise there.