> I think Reddit might be fundamentally flawed because of its voting system and its need for high moderation to make it workable.

Perhaps. Or perhaps it's groups of people that are fundamentally flawed.

> The only positive change i can think of is to cap active participants in a sub to a specific small number.

Which would break a significant number of use cases of reddit.

Whatsapp groups have no voting, typically pretty limited numbers of participants but can be hot flaming piles of garbage and a huge source of misinformation spreading around the world.