Online Dog Rescue Shelters... has anyone ever actually had success with these?

I have been trying for about 2 months now to adopt a dog through an online Rescue. I have filled out a few applications, sent emails, etc. - but NEVER hear a response. I have a nice home, I have previous experience (good) with being a pet owner. I have verifiable references, a job that would allow me to pay for unexpected vet bills, etc. Should I give up on these volunteer run groups who seem entirely ineffective and just purchase a dog from a breeder or visit my local shelter instead? After all of my research and attempts to communicate with and adopt a dog through one of these seemingly "real" rescue shelters online, I'm ready to advise folks against using these services. Any ideas/advice/comments? Real answers only, please.