> First world countries restrict trade all the time.

That's true. That doesn't mean it produces prosperity. Consider that those same countries impose sanctions on other countries to punish them.

How is a sanction different from protectionism?

Consider also a more comprehensive implementation of protectionism - Smoot-Hawley, which is credited as being a major cause of the Great Depression.

https://en.wikipedia.org/wiki/Smoot%E2%80%93Hawley_Tariff_Ac...

Those are a bare few data points that don't contemplate the history of technological and economic development. Historically, countries which want to develop their local industries protect them heavily when they're in a phase where they cannot compete against external forces until such point at which they can actually deal with the international market.

This has been one of the ways in which China has improved technological innovation at an incredibly fast pace.