Reactions to art are always subjective, and sometimes we just don't respond to specific performers, playwrights, musicians, etc. It is entirely possible that, consciously or not, Brantley does not respond to Williams' style of acting. This is a case in which I actually agree. I felt that Williams' performance in Blackbird was highly affected; whether or not it was a choice, it didn't work, and in my opinion it significantly diminished the play's power. Like Brantley, I had been floored by the Off-Broadway production 10 years ago; I wasn't even slightly shaken here. I think that is partially due to the larger playing space and partially due to Williams' lackluster performance. In any case, I would simply say that Brantley is entitled to his opinion of Williams -- which I share -- and we shouldn't be quick to pile on and suggest that he has some kind of personal animus towards her. He may just not respond to her as an actress.
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body