“It still kind of works without power” was an idea that kept hydraulic actuators in planes for a long time. But now most new planes are fly-by-wire (fully electric). Reliably stopping an electric car in an emergency should be a solvable problem.
So the fly by wire just means it is digital control to the hydraulic actuator instead of a physical cable running from the yoke or something to the actuator. They have not gotten rid of hydraulic actuators yet, they are working do that in the future but that is still a long ways out. Aircraft power systems also have significantly more redundancy so loss of control power is not a common mode failure due to have multiple dissimilar power sources.
The air brakes used on heavy vehicles (semi trucks, etc) have a very simple fail-safe. You need power to not brake. I.E. Air pressure is used to disengage the brakes. If you lose power/air pressure, the brakes engage and are stuck engaged.
