Bruce, I agree with everything in your post. Thanks for being so articulate.
As for dated, Ibsen's GHOSTS, for one example, is still performed today even though syphilis has been cured. That's because it's not really a play about the disease even if the disease is central to the story. To my mind, LVC is ultimately not about AIDS. It's about how gay men, and really all of us, form our own families, how we rally around and protect each other during the most impossible times and, on the other hand and ultimately, about the futility of life. Sound familiar?
Humor certainly dates and perhaps an argument can be made for that re LVC, though not true for me. Because of McNally's death, a friend posted a link on youtube to scenes of Nathan Lane in the original production, and I still found myself laughing out loud (and alternately weeping with sadness). Nothing is more subjective than humor.