I’m fine with an old person sounding like an old person as long as the work they do is solid.
Biden is equally mentally old as Trump, which is immaterial to biden being fit for office in this election and obvious from his first term.
Biden has been a great president who enacted consistent progressive policies, while Trump consistently hurt hundreds of millions of people and damaged the US.
Biden is certainly fit to be president again, and Harris can take over during the second term if anything happens.