Fascinating. I’d never heard that so I started reading about it online. It looks like it varies a lot depending on country. Many countries have no limits. Those that have limits set it at different ages (anywhere from 65 to 97). Some countries have flexible limits and it varies by rental agency. Some require older drivers to provide extra documentation that they are safe drivers and you have to buy their expensive insurance.
So the bottom line is that you have to shop around for rental agencies and/or places that don’t impose restrictions. Otherwise, I guess you’d have to rely on ridehsares or public transportation. Or convince a younger person to travel with you and be the driver. Depends on what kind of trip you’re taking. I rarely rent a car when I travel, but it definitely makes sense for certain kinds of trips.