While decentralization is taking place, it comes at the hand of new incumbents building large competitive moats around them. In the cases of the marketplaces you cite, there is massive aggregation at play, with Uber, Airbnb, etc, becoming the new gatekeepers. The flip side is more economic value is enjoyed by participants in the marketplace. But those marketplace owners are increasingly becoming monopolies in their own right. Ben Thompson has been writing about the increasing competitive advantage giants are gaining as scale increases, contrary to the popular notion that incumbents become more vulnerable as they grow. Sam Lessin just wrote about this too. Net net there is more value being created and shared among participants, but bad news for startups.