In terms of the skills you learn, I think critical thinking is certainly at the top of the list, but we often forget about a wide array of benefits that come with attending/graduating college.
Sure you could make more as a plumber or electrician or lineman than many jobs that require a college degree. Income is only a small piece of the benefits. As noted in the article, and this isn't just scare tactics, when unemployment rises, those with a college degree are much more likely to maintain and find employment. Blue collar jobs are often the first to go, whether through technological innovations (looking at you, truck drivers, when three self driving rigs get along), and moving jobs overseas. It's much more difficult to pivot when you have one primary skill and no degree.
It's also about job and overall life satisfaction. Many of the low paying jobs that get mentioned are helping or service professions. These people get the degree and enter into the field because they are passionate about helping people and their career. Many wouldn't find any satisfaction in a blue collar job and would gladly take pay cuts for a job that provides then with meaning and purpose, and longer lifespans as well.
Another crucial consideration is the social network you form, including the most important person in your social network: your spouse. Associative mating is a huge contributor to income inequality and perpetuating cycles of poverty.