Was William Shakespeare trying to present some sort of social message in Romeo and Juliet either directly or indirectly?
Ultimately, we cannot know whether William Shakespeare was trying to present some sort of social message in Romeo and Juliet either directly or indirectly. First, increasingly scholars are emphasizing the plural nature of authorship of the plays of "Shakespeare", pointing out that the plots are taken from earlier sources and much of the scripting was done in rehearsal and performance and editing. Given such authorship issues, discussion of internal psychological motives of an author is problematic.
Unlike mystery or morality plays, there does not appear an overt religious or moral viewpoint, and the "social problem" play as a genre really did not originate until the 19th century. Thus trying to read the play primarily in terms of some sort of intentional social message is probably inappropriate.
The conclusion of the play suggest that it was simply a story about two individuals without a general social critique:
For never was a story of more woe
Than this of Juliet and her Romeo.