Firefox (or OSs) should add a feature that randomly makes requests to a bunch of unrelated websites just to mess up their data collection and render it useless. This can only work if it's widely deployed.
Authorities will either look at the source code, compel the authors to explain how it works, push their own changes for the code in question, or just empirically monitor the random behavior and build models to filter such noise.
This is not a matter of "fix everything pill" tho, but a fight where we have to erode and degrade their capabilities, this is an arms race, you don't just stop fighting because the other side has got better weapons and systems, you develop your own gorilla capabilities
I have used it for years.