It is the businessmen and the politicians they buy to do their bidding that have ruined our economy. A businessman may know the business equation (revenues minus expenses equals profits). But an economist will tell you that expenses plus profits don't create a sustainable consumer market (revenues). Some businessmen are too concerned with making profits by cutting expenses to understand that the expenses side, which includes wages, is what mainly strengthens the consumer market. Businessmen tend to take the consumer market for granted. Easy credit is needed to make up the difference.
For the last 30 years, government has sided with business to suppress workers' wages.
The assault on labor started with Ronald Reagan's union busting in the 1980s and continued through all our free-trade policies that force American labor to compete with cheap foreign labor, like $1 per hour Chinese factory workers who slave under 19th-century labor standards while working with 21st-century technology.
Supply-side is not "supply and demand" economics. It is a pro-business political philosophy espoused by businessmen and their bought politicians to pass laws favorable to business at the expense of the U.S. worker.