Based on your own premise, Biden shouldn’t run either.
No question about it, Biden has no business running for or being POTUS, dementia or whatever he’s suffering from doesn’t improve over time, you only get worse.
As bad as Kamala Harris would be, she is the VP and should step up and become POTUS once Biden is removed, resigns or is taken out by the 25th amendment.
Biden doesn’t have that many years left, he should be in one of his mansions receiving private healthcare so he can be treated in private and live out whatever amount of life he has left.