In contrast to President Trump, President Moon Jae-in of South Korea has embraced a pro-labor program of higher wages and taxes. The early results have been discouraging. As President Trump leads a drive to slash taxes and pare back regulation, one major economy is taking a different approach. Under President Moon Jae-in, South Korea has raised taxes and the minimum wage in the name of economic growth. So far, it hasn’t worked out as planned. Growth has slowed, unemployment has risen and small-business owners like Moon Seung are complaining. Mr. Moon, founder of an auto parts maker called Dasung in...