I agree that the Fortune 500 are probably the primary clients of these consulting companies. I haven't dug into the problem, but I'm also willing to guess that FAANG doesn't really care about these services as much as the less technologically savvy ones in the Fortune 500.
The primary issue and ultimately the first step in solvency is still these companies abusing the system.
You can't very well stop companies from hiring other companies to solve their problems. I think that type of solution is probably impossibly hard to implement. Whereas if you simply stop these top few companies or create rules around who and how they apply, I think the problem is going to be greatly improved.
Like I said above. Lets push for solving the obvious problems first before applying pressure downstream.