I'm not going to comment on all the bull feces about who picked who and their skin color. My comment is only about P.J. Biden. Age had absolutely nothing to do with his capabilities. He was already showing signs of mental decline in 2020. He's never been the sharpest tool in the box or kitchen, but other than Tulsa Gabbert and Montana Gov Stephen Bullock, Biden was the only smart choice to run against incumbent Trump. They weren't flashy or popular with the media, so no one knew them. (they exhibited too much common sense).
Age had NOTHING to do with P.J. Biden's mental decline. My brother's Alzheimer's started when he was in his early 60's.