The voters aren't given unlimited choice as to who they can elect.
For example, to be eligibe to run for President, you must be Born in the United States and over the age of 35. I think to be eligible to run for the Senate, you must be over the age of 30. To be eligible to run as a Vice Presidential Candidate, you must meet the Presidental requirements above And be from a different State than the Presidental Candidate.
Term Limits are not a Limit on Democracy any more than any of these other limits are...Term limits would simply be an additional eligibility requirement: If you already served 3 terms in the Senate...then sorry, you're ineligible...Run for President, dog catcher, or some other position if you want to stay in public service.
Scott