There are nuances to the type of third parties we are talking about here. The type I'm discussing, something like the Lightning Channel and Plasma operators, t

There are nuances to the type of third parties we are talking about here. The type I'm discussing, something like the Lightning Channel and Plasma operators, these are roles that have cryptoeconomic properties that don't allow them to take over your wallet or refuse your service. edit: The base premise of having a smart-contract being itself the escrow is perfectly achievable. This doesn't mean that such a setup is the best solution to every use case and I believe that we'll see plenty of developments in this area in the coming years. For now the best approaches use game theory and computer science to reduce the amount of "trust" the parties must have in each other and the system itself but they are very much under active research & development.