While I’m not a Biden fan (cuz New Democrats gonna New Democrat, as we’re seeing now with the debt ceiling negotiations*), despite what polls state, I don’t think Biden’s age should be a factor in whether he should run again.
What Biden, after decades of tanking his presidential ambitions because he couldn’t keep his mouth shut, learned how to do was not run off at the mouth during the 2020 primary campaign (and the general too). He would do this by pausing before answering and restraining his enthusiasm and energy. Unfortunately, while this looks deliberate and thoughtful in someone younger, it just makes him look old, tired, and slow.
The second problem Biden faces is he doesn’t get nearly the amount of live TV that Trump did. Although I think this is, to a certain extent, by design–they are trying to be the anti-Trump and not be a constant, annoying presence–it hurts because most people never see him when he’s less locked-down. When you do see him engaged in back and forth with people (reporters and normies), he’s much more lively. He responds quicker and his voice has more inflection.
But, unless you see him in that kind of setting, he’s going to look like locked-down Joe.
This is a problem, and it could be fixed by getting Biden out and about more (and his Ireland trip clearly indicates he’s willing to do this).
*In Biden’s case, this is exacerbated by his tendency to ignore and delay when faced with something he’s just not that interested in or doesn’t know how to solve.