How so? Huxley certainly criticized modern progressive thinking in Brave New World. And in the quote you cite, it sounds like he's now critical of the view he once held.
Huxley never left progressivism.
He was a bright guy who saw the logical problems inherent in evolution theory, and thought he could get a pass by owning it, so to speak. Specifically, what he was doing was acknowledging the intellectual error of a specific product of progressivism, while refusing to reject the larger philosophical context on moral grounds.
This trick is not uncommon in the progressivist mind. It’s related to the progressivist delusion that self is god. Another, more common form of this delusion is the claim that communism works if the right people are in charge.