Quality of articles doesn't matter so much compared to the marketability of said articles and their sheer number. If you are a lawyer, a doctor, a real estate agent, and accountant, or someone with skills and knowledge that the general public could find useful on a day-to-day basis, you've got a shot.
If you're a fiction writer or a freelance writer that simply regurgitates other people's information, it's gonna be an uphill battle.
Either way, the sheer number of hubs out there, when combined with the general apathy of most people, means earning a living on Hubpages is extremely atypical and more of a fluke than anything else. So, if you need a certain paycheck every month, this is not a certain business venture.