I think this is an inaccurate portrayl. Even before I picked a field, let alone an advisor, I examined and thought about the job prospects and that was a factor in my choice. It is not as though the information were unavailable or even difficult to obtain. If a person makes a critical life choice like their field of study out of ignorance or whim then it is not really "the system" that is at fault if it turns out to be a suboptimal choice.
Now, there may be a few dishonest people in the system, and there are certainly many ignorant or biased people, and those people may even hold positions of power within the system. But the system itself is fundamentally not capable of hiding information about job prospects. If an individual enters the system without that knowledge then that individual made an important choice rather carelessly.
I don't know the statistics, but anecdotally my company sponsors visas and green-cards quite often, including several I have hired and others that I didn't hire but are on my team. The cost of sponsoring a visa is relatively minor if the employee is worth it.