It's not always so bad. I think a lot of it comes down to UX optimization.
My points of reference are http://colorblendy.com/ which gets +6,000 uniques per month and http://tweepsect.com/ which gets +25,000 uniques per month.
If you look at https://twitter.com/#!/search/realtime/tweepsect you can see that the quality of users is... not of the highest IQ, and yet they manage to figure it out. About once every 3-6 months I'll get someone @mentioning me saying "HOW DOES THIS WORK I DON'T EVEN" or something, but those are extreme exceptions.
When I first launched tweepsect, I had a lot more complaints and questions, but I iterated on it and tried to obsolete any recurring issue. It's been up for multiple years now and requires basically a few hours of maintenance per year. I'm happy to provide utility at near-zero effort for free.
That said, I completely agree about paying users. They're the best. When I was prototyping SocialGrapple, I invited +100 of my peers. The feedback was completely superficial and uncommitted. When I looked at how much time the people spent on the site, I realized that they weren't my target users and that the feedback was worthless. I shut down the beta and a month later I relaunched SocialGrapple with a monthly fee membership. The userbase completely changed--people really cared. I got people whose productivity and business was seriously impacted by the usefulness of my product to the point where I wrote custom views for specific users just to cater to their specific needs (until I could generalize it to everyone).