You may me right that there might have to be third parties for scalability. But depending on how this is done, you might not have to trust them in order to use them (in the worst case, they could refuse your transactions or delay them but not steal your money). So you might give up some privacy and rely a little on third parties for lower transaction fees or speed, but as long as everything is still using the blockchain you'd still have the choice to transact without a third party if you're willing to pay the premium for it (perhaps large or international remittances).