I'm glad not to be the only one that noticed that change, and to miss it.
I think that it happened around the time when the Mac version got the Application Frame.
I'm entering a feature request, http://feedback.photoshop.com/photoshop_family/topics/photoshop_jdi_re_establish_ctrl_cmd_ double_click_on_the_application_background_application_frame_to_create_a_new_document?rfm= 1 to re-establish at least that useful shortcut on the Feedback site. Please vote there and comment, and feel free to invite others to vote and weight on this missing feature.
Would you mind if I moved this discussion to the general forum to be more visible?
do it please
I'm not a Photoshop team member nor an Adobe employee, but a user like you. But you should vote on my suggestion to give it some weight, and invite others to do it as well!