That's a pretty weak criticism. Where are the jobs going to come from to employ the millions of people that used to be farmers (in 1875)? Where are the jobs going to come from to employ former delivery milkmen? Or what about the jobs for people that used to handle telephone call switching?
The same place they've always come from: economic dynamism. The solar industry, as one basic example, is adding 100,000 new jobs every four years at this point. In 20 years, that one industry will employ a million people - up from almost nothing in 2005.
We've got five million job openings presently. The labor market is quite healthy, with the U6 unemployment rate down to where it was before the recession.
Besides, unleashing all of that educated labor will result in increased innovation and economic growth, not less.