Those sites are all sellers market , no buyers there.
Not quite true for LinkedIn.
It's more of a buddy system - although some have called it another manifestation of the "Old Boy" network.
Obviously, successful and highly credentialed individuals will initially fare better at a place like LinkedIn than the average lumpen-worker
. Success attracts success
as the saying goes. But you can build a reputation and contacts even if you're not one of the 'shooting stars.' It will just take longer and require a bit more tact.
You need to approach LinkedIn more like you would a social network rather than a job/opportunity site. It's all about professional relationships. Unfortunately, generating 'relationships' has always been more time-consuming than just gathering 'leads.' But it's vastly more beneficial in the long run.
I only 'went in cold' for the first job I had after graduating college. Every other position I ever held after that was brought to my attention by somebody I knew. As I got to know more people, and they me, the money and opportunities that came my way got progressively better. So much so that I was eventually able to launch my own business with the financial resources and contacts I had accumulated over the years as a salaryman
I'm not endorsing the "Ya gotta know people, Kid!" school of success. But I'm also enough of a realist to realize that most people prefer to work with people they know - or their friends know - rather than a complete stranger.