I'd say that it's perhaps more tied to moderation. Reddit communities vary dramatically in quality of discussion and one thing that seems to separate the highest quality from the lowest is heavy moderation. AskHistorians for example is extremely strict and has very high quality answers. Another example that's strict in a different way is CasualUK, where even vague references to politics or politicians is an immediate day ban (I was banned for making a joke that someone looked like a particular politician) and this results in a high quality "discussion" (the goal is not debate but fun friendly chats and it achieves that perfectly).
edit - evidence on the voting system not always helping is that quick, low effort posts and comments quickly rise to the top and drown out all other things. To the point where banning direct image posts so users have to click twice rather than once makes a difference in what's posted and rises.
edit - evidence on the voting system not always helping is that quick, low effort posts and comments quickly rise to the top and drown out all other things. To the point where banning direct image posts so users have to click twice rather than once makes a difference in what's posted and rises.