Making it FOSS wouldn’t solve the problem, because FOSS tools can still be used by capitalists to displace workers and erode worker bargaining power.
This is true of pretty much EVERY tool, but never has a tool had the potential to negatively impact so many in such a diversity of roles.
So again, the problem isn’t closed source, the problem is capitalism. If you fixed the problems of capitalism, then all software tools would naturally be FOSS, but that’s a product of fixing the problems, not the mechanism to fix the problems.