Yeah, DNT was dead on arrival. I have no clue why the internet powers that be though that would be effective in any way. I guess its more of a feel good action.
A DNT-style browser feature with legal weight behind it would have been miles better. Your browser could present a consistent interface for every website that requests consent, and allow you to set global defaults, etc.
Maybe it's a harder issue to solve with a UI (third party cookies, subdomain cookies etc.) Maybe they just haven't gotten around to it (I used to set the global "site im visiting" cookie pref but since they added the "intelligent" cross site tracking protection that option seems to be gone..