Hard to say if this satirical or not ("Etherium") but will respond in good faith.
1. Same argument can be used in the opposite way, you can verify the counter party will act as expect, there is no need for costly litigation as backstop.
2. An engineer reviewing a contract once will not be more expensive than hiring a full time banker to review each transaction or a lawyer to pursue a legal battle.
3. Decentralization and regulation are not mutually exclusive.