Harris performs worse than Biden in polling (that could change if she actually became the candidate, but that's not certain). And there really isn't anyone else that is realistic- Harris is the leading choice.
The age thing probably will get nullified if Trump is the nominee. Trump's not young either and less healthy.
The Hunter Biden stuff is largely irrelevant. Most voters don't care about that stuff.
The thing that keeps me up at night at this point is Cornel West and No Labels.