Romeo and Juliet do display some loyalty to each other, but it is not the main theme of the play. For example, Romeo risks his life to be with Juliet, and Juliet chooses to die rather than marry someone else. However, these acts of loyalty are ultimately not enough to save them from their tragic fate.
The main theme of Romeo and Juliet is the conflict between love and fate. The two lovers are caught up in a tragic web of fate that leads them to their deaths. This theme is explored through the use of symbolism, imagery, and foreshadowing. For example, the play is full of references to light and darkness, which symbolize the lovers' hope for a bright future and their eventual downfall.
In conclusion, while Romeo and Juliet do display some loyalty to each other, it is not the main theme of the play. The main theme of the play is the tragic conflict between love and fate.