Well that’s not true at all. I don’t think most of us are going on social media to communicate with billions of people. If we can communicate with tens of thousands of people, or perhaps less than that, but those are high quality communications, that’s good enough for many or most of us.

Which is to say, quality of other users, quantity of users, and quality of service are all important when trying to evaluate the overall quality of any social media provider.

Of course your goal could be different if all you want is exposure. If you want to advertise, then large numbers of users might be your priority. But most of us are not doing that.