Of course Do Not Track is meaningless.
It has always been meaningless. It's a voluntary thing which says nothing at all, and isn't legally binding. It's complete drivel. It's something the industry put out to give the illusion of giving a shit about what we want.
Want to prevent tracking? Don't let the packets happen in the first place. Use things like NoScript, Request Policy and HTTP Switchboard to deny the access entirely.
Treat this stuff like the shit that it is ... intrusive advertising and tracking about everything you do.
The only way to win is block as much of this crap from your browser as you can. You don't owe these companies this data, and the less you provide to them the better.
And when they whine and bitch about their revenue stream and their terms of service ... well, too damned bad. You aren't required to pull in any packets you don't wish to.
Once you start using these blocking plugins, you'll be amazed at just how much crap is actually embedded in most every page. One some sites, literally dozens of 3rd parties ... none of whom give a shit about your Do Not Track setting. So just block them entirely.