That brings back some memories of a former US president. https://youtube.com/watch?v=Yq7FKO5DlV0

And to answer OP question :

No, because democracy. But we shouldn't vote for these old guys

certainly. even lower. Some people can be vigorous in their seventies but they are not the majority, 50's many go down. That is one problem with raising the retirement age in general. There is only a subset that can keep working as age goes up.

Needs to be a little lower

Not for House or Senate. Age just isn't a close enough metric for what you're trying to fix.

If you're concerned with age-related decline, vote them out if you see signs of it, or if they would reach whatever age your limit is during the term.

If you're concerned about longevity in office, use term limits or reform campaign finance such that longevity in office doesn't grant too high of an incumbent advantage.

SCOTUS, sure. I think Canada has appointments until 75. Does not seem meaningfully different from appointments for life except less randomness on open slots.

Their age doesn't affect me in the slightest.

Yep, no question.

No. Because as time goes on, 75 will be younger and younger.

No, because in a proper democracy any representative could be removed from office at anytime solely by their constituents voting to remove them. No I don't mean during a predetermined election cycle. I mean at any time.

That way each community can decide if someone should be out of office, and it transfers power back into the hands of the people rather than their representatives.

No. That's age discrimination. If you're concerned that a person could be suffering from mental degradation, require annual testing for it. I know folks in their 90's who are better critical thinkers than a lot of 20-somethings.

The problem we have is not that a bunch of old people run the country. It's that a bunch of young people put them there because they were the only real choices they had. Fix the two-party system first by employing ranked-choice voting. That will break the stranglehold that Republicans and Democrats have on the US political system.

Yep.

Term limits please