Earlier quoted context omitted.
The problem isn't just his age, it's his decrepitude, both physical and mental. I know people in their 90s who are able to speak clearly at any hour of the day...
Biden was never the quickest guy (or tongue) in the room. During Obama's term, he was legendary for putting rooms to sleep with plodding, off-topic monologues where he set up irrelevant straw-men and then knocked them down. Obama was, by far, the quicker of the two. Time has probably not improved matters, but it's going a bit far to say Biden's declining sharply. Even in his prime, Biden might have stuttered and stum…
Harris has been a ghost for 4 years, after dismally losing the 2020 primary, and being selected ostensibly because of her group identity.