Really? That's like saying there's little to no money to be made in entrepreneurship today. Are you saying everyone on AMZN operates their business at 0% or less net profit margin? Because that's essentially what you are saying.
To stand a chance at making some money as a small business (and I'm saying the more typical "some money", not the "strike the motherlode" type language many of the make.money.fast type scams promote), you have to have a good product idea, and do the full work of the low-margin retail business, with all that this entails.
In this regard I do imagine it's possible to make some money via Amazon with a traditional retail business. But even though it's the behemoth of American e-commerce, Amazon probably should not be a product's only Internet retail outlet. (You should probably have your own e-commerce site for a start... and other more focused outlets, especially if they fit a product's niche -- like, say, Newegg for a computing oriented product -- should also be pursued.)