> A "just say yes" attitude leads to certain disaster
Disaster's a possibility. But if an idea has a 1% chance of success, "just say no" usually assures failure, whereas "just say yes" is a shot at that 1% chance.
If there us a 99% chance if faulure, the rational response is no unless the rewards are absolutely, insanely huge (at least about 200x the cost of every resource used) and the org can take the failure.