There's really no evidence of dementia. If you knew anything about dementia or spent any time around dementia patients you wouldn't make that comment.
I think there's some evidence that he's beginning to slow down cognitively as everyone does as they get older but there's no indication of dementia or a lack of mental capacity.
Also the media tore into anyone who made comments about biden who actually had dementia for years. So maybe people are just afraid of being attacked by the media now if they bring it up again