Blunt tools shouldn’t be used for complex real-world things. Other examples would be mandatory sentencing in courts (you should let the judge assess the particular situation), or things like “I don’t go out with guys under 160cm” (you should get to know him).
Just because someone is in their 70s, doesn’t mean they can’t lead. Not with any certainty. In some cases it does, but the political process should have the flexibility to deal with each case.
Look at Deng: he was mid-70s to mid-80s when he was in power and he improved the lives of 10⁸ or 10⁹ people.
Voting can happen like that, but we don’t let super qualified 34 year olds run for president and we shouldn’t let 70 year olds run either.
I don’t see anything wrong with leaders under 34 per se