In an ideal world we could detect those patterns programmatically but as you hinted, there is the question of "when is it considered a dark pattern and when is it only clever marketing?".
The answer is actually clear - it's always "dark pattern" from the POV of the user, and it's always "clever marketing" from the POV of the business applying it. Each side draws the line so far in the direction of the other that there isn't any easy compromise.