Maybe there's just too many people who want to become dentists; resulting in too much demand and too high prices for dentists diplomas, and too many dentists for prices on their work to justify these diploma costs?

Why not just allow everyone with a medical dimploma from a 1st world country to come, get GC at the airport, and get to job the next day? What are the downsides, except liberals around the world nagging again that U.S. were robbing them?