H1b program doesnt hire that many workers first of all its a tiny fraction of workers. Secondly employers need to apply for the visa for the position before they can search overseas.

Yes, but only because there's an actual cap of how many H1b are allowed each year.

If thats getting approved then there isnt the local talent to fill those roles.

There is no such requirement for a visa being approved.....

This doesnt drive down the local labour costs because its still easier to hire locally than import labour via h1b system.

This ignores the real value of h1b for management. Besides being able to pay less for talent, you also have a lot more control over the worker. They aren't able to take better offers or join/start labor organizations, and turn around is often one most costly aspects of jobs with higher education levels. Locking in a highly educated professional with little to no room for advancement for 6 years is going to be highly attractive to any manager.

There is evidence I found suggests the h1b workers are paid 15-30% below market and that should be enforced better.

The real problem is that the 15-30% likely isn't accounting for the experience of the worker. I work in a field that requires a lot of education and licensing, and when initially starting a career you really should be getting about a 20-25% raise every two to three years. A lot of the times this is done by getting offers from different organizations, which just isn't an option for H1b workers.

But its still a win win for all parties, employer fills their role, employee gets a high paying job

I think it's naive to believe that this isn't a ploy for employers to pay less for specialized labour. The employer wins, the H1b worker only wins in a sense that they are being exploited in a currency with higher value, and local labour loses a worker that could join a labour organization.

Especially the people in here calling it indentured servitude.

I mean, it's basically as close to indentured servitude as you could get in 21 century America "a system where individuals contracted to work for a set period, typically in exchange for passage to a new country, room, board, and sometimes other benefits like land or tools. "

fine and doesnt seem to be harming wages or exploiting and enslaving foreign workers.

Eh, I would say the only thing stopping it from doing so on a much greater scale in that there is a cap on the how many H1b are made available...a cap which a lot of tech moguls are trying to dramatically elevate.