I use Cookie AutoDelete (I use only Firefox, but that is irrelevant in this context.) Deleting all cookies (one could also use white^Hallow lists) works 98% fine. The problem is local storage. Pages can store the same (and more) information as in cookies in local storage. There is no add-on API to manipulate local storage. At the moment only an estimated 2% of all web sites use local storage to store tracking information. But if cookies get widely ignored/deleted, I am sure that will change.