Like, the site owners/employees/admins/mods are the only ones who choose what to post(and hopefully not extremely bias and a good spread of topics), but the users can still upvote/downvote the post as well as comment and all that?

I like the aggregation mark down style of these sites, but I am not sure about the curation being purely user based. I am curious if the users having a large majority control of the curation hurts the quality, and I’d like to see comparisons if they exist.