Just as an example off the top of my head:
Warren Buffet is 95, Munger was 99 at the age of his death. Both would have outperformed Biden in their 90s, IMO.
Thomas Sowell would also "run circles around" Biden at 95.
But, I'm also good with setting an age restriction. Transparent cognitive tests would be better, codified into an automatic 25A, perhaps.