Not everyone has the skills of an engineer. Not everyone is interested in engineering. And why should you suppose that good, steady solid blue collar work is either unnecessary in today's economy or worth less as a personal choice at any time?The jobs those semi-skilled workers lost are being performed by Asians and Latin Americans today. Do you suppose the level of education is that much higher in Asia or Latin America?
The economy grows when we make things, not just buy them. A vibrant Middle Class demands steady, good paying manufacturing work. Textiles, electronics and transportation still require manufacturing. That's served as a steady and reliable gateway to socio-economic advancement for decades.
Soon, the transportation costs of manufacturing in Asia and Latin America will dwarf the savings in lower wages and lax environmental compliance and the manufacturing base might well return to America. But necessity is the Mother of Invention. Someone will figure out how to keep costs down. They certainly did with American labor.
Do factory workers make more money than engineers? I never heard so.
Not everyone is interested in being a bored factory worker in a deadly repetitive job either. But you claimed that we make money by making things. This is patently untrue. What did Bill Gates make?
Blue collar work is what it is. American workers are very productive, thus our higher wages. Chinese workers are unproductive, thus lower wages. But our wage scales are exaggerated by union rules, Labor Dept rules, OSHA, etc etc. Get rid of that crap and the American worker will outperform the Asian worker every time.