You are exactly right that too many students go to college and not enough go to voc-tech. Many of the college degrees are absolutely worthless. Many of the students were never good students in junior high or high school and becoming a college student is never going to magically make them a good student.
Also, it is far less likely that one’s job as a plumber or electrician will ever be outsourced the way other careers have been.
The problem facing the trades was never outsourcing; it was importing braceros to do the work. I see them doing just about everything but electrician work; plumbers and carpenters seem to prefer them as assistants to young Americans. A friend described how he knew he’d eventually lose his roofing job because his firm was hiring lots of braceros, even they had no idea how to use the tools. The company would just train them instead of Americans; the only work left for Americans was the best of them could stay on as foremen - if they spoke Spanish.