There is much here to say. I think that one of the fundamental premises of the play is the idea that mutability is an integral part of the human experience. Kushner is arguing that the cleave to tradition and a view of the world that does not understand the fundamental role of change or transformation is bound to fail. From the most political and personal of views, this is evident. Consider Prior's stinging rebuke to the angels who desire a static reality:
We can't just stop. We're not rocks— progress, migration, motion is ... modernity. It's animate, it's what living things do.
This statement that change is intrinsic to human beings is how the play progresses through the eyes of each character. Prior must accept the change that is impacting his life and his body. Louis wishes to go back to a time where things were more clear cut, but he must recognize that change has scarred him and he must accept this condition. Joe's reverence for Reagan is something that acquires a nostalgic reality, a powerful rebuke towards the exceptionalism felt at the time. The Conservative worship of the time of Reagan is in stark contrast to the changing landscape in which both gay and straight people find themselves. In this political expression, the fundamental idea of the drama is evident in that change is intrinsic to what it means to be human.