I mean I guess I'd point out the members of his own party going into panic mode calling it "a disaster" etc. The blank stares with his mouth open, him not being able finish sentences numerous times. These are things being pointed out by people who want him to win! This isn't just "old and sleepy". You don't have to offer a diagnosis of dementia to accept that there's severe diminishment of mental acuity.
I don't necessarily disagree about the Trump point but again, even people who are fully on team Biden are pointing out how much sharper Trump was. (Not honest mind you--that's not something Trump seems too interested in or maybe even is capable of--but the contrast in how "with it" each of them were was "staggering" according to some major Dem donors).
It's a little weird you'd think someone deluding themselves a bit also couldn't be trying to come to conclusions in good faith. As humans, we subtlety justify a lot to ourselves in order to have our worldview validated. Confirmation bias, etc are all tools we use. I don't think you're intentions are dishonorable, I think you're seeing thing skewed a bit so they look just close enough to how you want them to look. Again, that's my opinion on your view. And of course I'm sure you can and will dismiss it and that's fine.