I agree this would have somehow been a good idea…But after 7 movies with the same opening protocol, it would be weird to change it now.
Not change, just slightly adapt it to the current story’s mood, which I guess will be darker than the last one.
If it worked for Empire Strikes Back and Revenge of the Sith with their comparatively darker moods, I see no reason it wouldn’t work for The Last Jedi. I’ll go so far as to say having to change the music to fit a darker mood is a lazy way out in creating that mood.