Forget marketing channels, marketing pieces, whether or not cash buyers are serious, etc.; the fundamental problem with wholesaling in so many markets is that the economic situation of Americans in late 2015 is vastly different than it was during the salad days when wholesalers were "killing it."
Economic conditions are starkly different. After 2008, credit was tight, which made it more difficult to get a mortgage loan. All the while, large layoffs were happening in droves, house values were plummeting, and due to the credit crunch, a lot of homeowners couldn't refinance. The result: many homeowners were clamoring to get out from under their houses. It was during this swirl of post-2008 economic misfortune that some wholesalers in certain moribund housing markets were making a fortune.
Unfortunately, those economic conditions don't exist across the United States anymore. The same deep pool of motivated (i.e. desperate) sellers simply doesn't exist anymore in most markets (less inventory), which is why a lot of the big wholesalers have turned towards selling systems/how-to information for aspiring wholesalers. Look, no system is going to overcome unfavorable economic conditions and market realities.
Are there still wholesale deals to be had? Sure there are, and some markets are more favorable than others, but there are a lot fewer, all the while a many more wholesalers of varying abilities and levels of commitment have entered the field - increasing competition.
Now that I've said my piece, I'll sit back and await the you're-too-negative reply posts.