> we must distinguish between "good voter suppression", like banning votes from toddlers

Banning votes from toddlers is not as clear cut a point as you make it look like.

As a thought experiment: imagine an extreme society made 15% of childless adults, 5% of young parents and 80% of toddlers.

Would it make sense/be fair if the 15% of childless adults could pass laws that remove voting rights for life from anyone that piss their pants in public whatever their age ?

You could end up in a situation where 20 years later 90% of the adults of the country have no voting rights. Finding a way (setting the 5% of parents as representatives ?) to mitigate these kind of issues is generally important, which is why there's no cut and dry "good" voter suppression, only compromises.

Your preoccupations seem to be centered on protecting the system from demagoguery and outside influences, which is a valid POV, but that can't be the only angle nor the central focus. Even if 80% of the population was provably dumb, you'll still need a system that takes their voice into account to avoid the country getting overthrown or become a dictatorship.

> universally

Honestly I don't like that word, and it removes a lot of nuance that is utterly needed for politics and ruling systems. There is almost nothing universal, especially when it comes to "good" and "bad".