While true, the question should be: is each European nation/the EU collectively doing those restrictions sensibly, or poorly?
If done in a similar fashion as the US has chosen, i.e. due to incoherent populism, it would limit the number of competent e.g. Americas, Canadians, South Africans etc. from joining the European workforce.
If done in a sensible fashion, it would only exclude the would-be migrants from those (or other) countries who have shown a wanton disregard for democracy and other constitutionally required values.
A nitpick here, but "visa" gets tossed around a lot. A visa is a document which allows you to request permission to enter a country for some purpose. To work in a country you need a work and/or residency permit. Even in the US, there are situations where you can work with a an expired visa, provided your other immigration documents are current. But if you leave, you need a new one. Similarly UK citizens can still work in some European countries without a visa, because there is no requirement for them to enter with one (but the officer at the border might still refuse entry).
Again, depends on the country. Switzerland (which I appreciate is not in the EU) does not require visas for many "friendly" 3rd countries even if the person is coming to work.
What's really interesting to see is your blindness to that self destruction.