It's the words.
George: You take the trouble to construct a civilization, to build a society based on the principles of... of principle. You make government and art and realize that they are, must be, both the same. You bring things to the saddest of all points, to the point where there is something to lose. Then, all at once, through all the music, through all the sensible sounds of men building, attempting, comes the Dies Irae. And what is it? What does the trumpet sound? Up yours.
Virginia Woolf's story is practically secondary, what with the many long dialogues, stories and digressions. It could hit its marks in half the 3+ hour running time, but only to the play's great impoverishment. As another Edward Albee character once said, "Sometimes a person has to go a very long distance out of his way to come back a short distance correctly."
For there is a point to be taken from the speechifying in this behemoth, something about the lies we tell ourselves and each other, including on the goodness of people. Convention holds that the protagonists of a book/movie/play, the mirror held up to nature, must be likable and/or sympathetic. Balls to that. Some people, many people, are, to quote the same character again, "mean, stupid, unwashed, misanthropic, cheap, drunken bag[s] of garbage." All the drama asks is that they clutch our morbid attent, vigorously and without relent.
George: Yes, Martha? Can I get you something?
Martha: Ah… well, sure! You can, um, light my cigarette, if you're of a mind to.
George: No. There are limits. I mean, a man can put up with only so much without he descends a rung or two on the, uh, old evolutionary ladder, which is up your [Nick's] line. Now, I will, uh, hold your hand when it's dark and you're afraid of the boogeyman, and I will tote your gin bottles out after midnight so no one can see, but I will not light your cigarette. And that, as they say, is that.
One can parse the text for such a meaning--the above is but a first try--but that's to miss enjoying the words. And this isn't to say they exist for their own sake: far be it. The witty, pedantic repartee is a facade to hide the desperation unmasked at play's end, which gets back to the lies being told. There is no better way to expose illusion than a smokescreen.