Smaller communities may mean fewer posts, but once a community hits a critical limit, it's still more posts than most people will read in a day.
This is only really an issue for really niche communities that haven't migrated here yet, and if all they find here when they come to explore is the exact same posts as on Reddit, but with no comments, then what's even the point of moving?
If they didn't come out of the principle of what Reddit is doing, then it will be the content that ultimately makes them move. And that content needs to be different, and better, than what they can get on Reddit. Not the same, but with zero comments.