The professional class already can negotiate for pay and working conditions because they're hard to replace. For example, I negotiated my salary up by 5k at the start and receive good annual raises because my skillset/expertise is hard to replace.

We also saw during the great resignation how employers were forced to pay better because they were having trouble finding people.

If employers have a credible threat of not being able to find people, they will have no choice but to offer better pay and better working conditions. As for how we achieve that, I'm personally in favor of a few policies:

YIMBYism and land value taxes to solve the housing crisis, so that average folks aren't so squeezed on cost of housing
Universal basic income to decouple paying rent and putting food on that table from jobs
Public works/employment programs for activities that produce positive externalities, e.g., subsidies for FOSS software, more public research grants, subsidies for rewilding efforts, etc.

The general idea being that if you don't desperately need your employer to maintain a basic level of existence, they will have much less leverage over you. If you can credibly threaten to leave and go plant trees or write FOSS software or pursue higher education, your boss will need to offer you more.

Bonus point as, once housing is cheaper and once jobs pay better, people can have more in their savings accounts. This alone makes them less dependent as well, because they can survive longer and more comfortably without a job. For instance, if my boss mistreated me today, I could quit and coast on savings for a while until I found a new job. Those living paycheck-to-paycheck are living in a constant state of exploitation that is extremely ripe for exploitation. Destroy the desperation and you destroy the exploitability.