Term limits are anti-democratic. You're saying that we can't trust the voters, so we need a rule; like they're children. If you think the voters are the problem, then you don't believe in democracy.
The mistake is believing that the situation with McConnell and the other dinosaurs is what the voters chose, rather than a system where the voters don't get a meaningful choice. A system where the Senate itself is undemocratic. Not to mention the electoral college. Is McConnell's long carrier due to his popularity in KY, or his popularity with the donor class?
We need more democracy in our democracy, not less.