There shouldn't be an age limit, there should be a term limit. The problem isn't really that people are old, that's just a symptom. The problem is that it's the same people in government, decade after decade.
Also building alliances takes time, it used to be that politicians in DC were all friends with each other, which means they could go to the bar after work and figure things out together over some drinks. Now days any politician seen talking to someone of the "opposing" party is deemed a traitor and vilified by the 24hr news media.
They were a tiny percentage of the budget, and it was a small price to pay for functioning government.
And term limits will make it worse.
This isn't some theoretical, research has been done on states that have implemented term limits, everything got worse.
OK imagine senators have a 2 term max, 12 years. They are now 100% incentivized to plan for their next job and not actually care about being a senator. We already see this with roles that are appointed by the administration, FCC commissioners are famous for this. Go from industry -> government -> higher paid industry role, utilizing the connections one gained while in government.
Hah, I wish we could hold on to engineers for 4-5 years…