An opinion: The most serious threats to user privacy from advertising companies are the "features" of the browser that allow data to be sent to or from the users computer without any input from the user. In other words, the features that let developers of websites trigger GET and POST, to "push" media to the users computer and allowing "pulling" user data indiscrinately, without explicit consent and sometimes without the knowledge of the user.

For example, there is the feature of automatically loading resources, such as images. No user input required. There is the feature of automatically loading the contents of iframes. No user input required. There is the feature of cookie headers sent automatically. No user input required. There is the feature of XMLHttpRequest triggered through Javascript. No user input required. There is support for HTTP/2. Imagine websites pushing media to users computers with greater efficiency than ever before (advertisers rejoice). No user input required.

If one is serious about regaining control over the sending of user data to these corporations and websites ("privacy"), then IMO one needs a browser that either lacks or can disable the features above and any others that allow media to be "pushed" to the user without any user input. Such a browser would only execute GET or POST upon user input, not upon input from other sources, such as websites.

Perhaps users could have two browsers: one for commercial activity and running "web apps" and another for non-commercial activity, which may not need to be default compatible with "web apps" that push media to the user. This is an alternative to having to become an expert in browser settings.

Instead of disabling features or installing add-ons, the later browser is incapable of pushing unsolicited media or leaking user data because it lacks the necessary features to do so. (I have been using such a browser for many years now. While this is probably not for everybody, I like it.)