It's worth pointing out that almost none of the work in the examples in your first paragraph is done by someone straight out of school with only a college degree. Surgeons, lawyers and engineers typically go through years of on the job training before they are allowed to install heart values, prepare complex trusts or design pacemakers. Which says little about the value of the college education, other than that it serves as a filter before someone can receive the hands on training and mentorship that is critical to performing those tasks.
If surgeons/lawyers/engineers say "I'm only go to offer an apprenticeship to someone who went to school for eight years like I did", then that's fine, it's their choice of who to invest their time with. But it doesn't prove that a traditional four year education is a necessary prerequisite to being able to do any of those jobs.
Proof and necessity are logical constructs. In the messy real world we deal with judgement and experience. The burden is on those who want contrary judgements to be given weight to point to experience and rationales that justify its acceptence, e.g. to reason from sound statistical evidence.
It's not enough to say, "Hume proved we can't really know anything about the world of things." The claim is not that the current system is perfect. My claim is that the system is better than the alternative for certain vocations and that engineering is one if them.
If surgeons/lawyers/engineers say "I'm only go to offer an apprenticeship to someone who went to school for eight years like I did", then that's fine, it's their choice of who to invest their time with. But it doesn't prove that a traditional four year education is a necessary prerequisite to being able to do any of those jobs.