It works because they just outsorced things like defense or healthcare.

Is easy to brag about how you don't need technology when somewhere a team of extremely sophisticated machines are deployed pointing towards the sky to save the day in case that you would be bombed. An entirely independent Amish nation would be probably eaten by their neighbors or by the market in months.

And their life style proven to be very fragile acting against things like Covid. They suffer also still from occasional outbreaks of Measles and Polio that were eliminated in the rest of US by the use of vaccines. Living in a different century can seem idyllic, but has the price of dying younger.