It certainly isn't a complete solution, but it probably did reduce the number of ad networks that tracked you. So yes, I guess you could say it works?
5%? Nah, I'll pass; I don't want to spend my last six months in agony, so it's not worth it (i.e., bad trade-off). 95%? Hell yes, sign me up. Your own analogy supports what I said earlier.
On a side note, the statement "Chemotherapy will probably cure your cancer" is also not true and shows a bit of ignorance re cancer therapies in general.
It is trash, but at least it is something.
Compelling arguments in favor.