Escalators vs elevators is maybe a good example of the concept in theory, but in practice escalators are the worse design of the two, and they don't necessarily compete anyway.

Escalators are either slightly faster stairs or stairs for the sedentary. Their only practical advantage is clearing high-volume areas quickly, like transit stations. But otherwise, they are worse stairs - costly, narrow, power consuming mechanical stairs that require regular maintenance. Elevators are an accessibility feature. They allow easy movement of the handicapped and large cargo, and can move many, many floors quickly. Nobody is taking escalators to the 57th floor of a building.

Not to say escalators don't have that advantage of failing in a useful way, just that they don't do anything stairs don't already do. Nothing else really does what elevators do.

Better example may be, say, ebikes or hybrid cars, provided they don't lock up the conventional drive system in the event the electric portion fails.