As for H1-Bs, the reason Google, Facebook, Apple, Amazon, Microsoft, et al, hire them is not to lock in slaves at low wages who can't leave. Yes, there are companies that do this, but the reality is, tech companies love to hire new advanced degree graduates and a large chunk of those with master degrees and above are immigrants.
If I want to hire a bunch of Phds in machine learning, optics, materials engineering, etc chances are they will be F-1 Visas and you won't see many native born in these programs in proportion to their representation in the population. This is just an uncomfortable fact.
What I find interesting is, conservatives will often tout this "pipeline problem" to explain away low representation of women and minorities in STEM jobs -- as a natural outcome that nothing should be done about it. However, when it comes to native born American (primarily white) males, who have their own "pipeline problem" at the advanced degree level relative to legal immigrants, you see them crying for government policy changes to protect what they assume to be their birthright privilege.
Most of the H1-Bs I have worked with, including my wife, were exceedingly talented, and hired by companies for their talent, not low wage slaves. This may not be true of consulting firms, but we can address those who abuse the system without lowering the overall number of H1-Bs allow -- that should be defined by market demand and right now, with unemployment at 2% in the STEM fields and salary inflation going through the roof, along with valuations, I question how much "protection" citizens need against importing the smartest people from around the world.
I leave you with this: https://www.youtube.com/watch?v=NK0Y9j_CGgM