Of course there is ageism inherent in some posts.
He runs; he cycles; he does weights, Films of him on, for example, plane steps show him practically running up and down them. His schedule for recent visits to Ukraine and Poland, and to Northern Ireland and Ireland don’t suggest that he tires easily. He appears to have no balance issues.
So where does doddery come from?
If people are referring to his gaffes, they don’t seem to have worsened with age; he has been renowned for them pretty much his entire political career. The same is true for the pauses in his speech, which are the result of controlling a stammer.
He’s a skilled consensus builder, which, it feels to me, is no bad thing in the present day USA. I do have issues with some of his domestic and foreign policy positions, which I’m happy to debate.
My only real gripe is that he hasn’t sent me anywhere near enough stimulus checks [sic], bother him, although that suggests the American economy is in better shape than it was under his predecessor.