You would need to get another job, unlike a citizen. It need not be said how that's a significant barrier to resisting your employer, no?

Another job willing to do the paperwork, willing to sponsor, that has access to an immigration lawyer. It's not just 'finding a job' it's finding a job at a company willing/able to do all that. It's definitely a much higher bar.

The paperwork is far less onerous than for sponsoring a new immigrant.

In my experience recruiters saw H1B transfers as routine but would ghost me once I explained that I required a new visa sponsorship since I worked or a cap-exempt employer and could not simply transfer.

The point is that it is a non-zero amount of effort and cost, creating a second class of employees.

While temporary residents do have fewer rights than permanent residents or citizens, the characterisation of us as indentured servants is just absurd. Those of us working in tech are pretty privileged overall - the median software developer salary is above the 90th percentile!

That you are "pretty privileged" is a value judgment of your own and is irrelevant to the deleterious effects that the conditions of your employment create on the industry at large.

Yes: software developer incomes are high. But simultaneously, unemployment amongst CS grads at American universities is also high.

Shrug. Having 10 years of experience when I moved here I don’t think I was competing with recent CS grads at any point. I did however share that experience with the newly graduated US junior developers I mentored.

I am specifically talking about tech, I personally knew many H1B folks that worked insane hours literally so that they were seen as ultra productive and wouldn't get cut.

That sounds like a really unhealthy workplace. Fortunately that was not my experience working in tech on a visa.