IMO, the meaning is simple... if you are an experienced person then they can make more money on your professional efforts. There can be many other reasons.
As someone said, go to offervault and see if there are offers that match your site, then sign up for that network and tell them you have at least 18 months CPA experience with 2 or 3 other top networks. Don't worry, every business runs on small and big lies. You will get plenty of info on how to face their phone call. It is also a good idea to call them immediately and talk candidly.
I think, if you resubmit to this same network again after 2 weeks and mention 2 years' successful experience, they will let you in.... simply call them first and ask to connect you to a manager.
Good luck to you!