Service and testing requirements for voting have good intentions but are likely bad ideas.
As with any such rules, imagine the worst possible person in charge of said rule.
Like the founders, we should make rules that are fairly robust to bad actors (tyranny, of course would outright ignore the rules) and not dependent on always having good, honorable persons in office.
(Obviously they weren't perfect given FDR's example of ignoring precedent and the plain language of the constitution. However, I would say it still qualifies as "fairly robust" given how long it took to get to that point.)