this is certainaly debatable
in every subject I'm a... subject matter expert in: it's been pretty bad
Today I hit for the first time a site that made it as easy to Accept or Reject startrek.com also many sites now offer option to delete my account and even JS APIs for tracking now have options for GDPR to not store private data. So YES things improved but are not perfect, to blame is not the law but the jerks.
Browser vendors tried to establish such a standard but it pretty much died when Microsoft enabled it by default for IE9 and some ad brokers began to claim that they can now ignore DNT because it doesn't actually reflect user intent anymore. (see https://www.theregister.com/2015/04/03/microsoft_reverses_ie...)
With that it became deprecated. Thank you, Microsoft and Yahoo.
The general sentiment seems to be that "if you want it, you want it, and who would want it explictly off?"