An important difference is that cruise control is simpler to understand. It’s a basic mechanic dressed up as a driver aid. A smaller slice of the population will incorrectly use cruise control.
FSD is a driver aid dressed up as… well, “Full Self-Driving.” It’s not Full, and it’s not Self-Driving. It’s mostly functional in limited circumstances and even then requires driver attention.
I think another good example is how people would never allow a Stasi agent to live in their house, unless the Stasi agent was redefined as a slew of websites, a collection of disparate laws, and multiple steps involving technology.