My summer bus to-and-fro' work reading is Why Religion Matters: The Fate of the Human Spirit in an Age of Disbelief by Huston Smith. His The World's Religions probably rests on more UU congregational library shelves than the Bible.
I'm digging into it, and it is a plain and popular (but hardly simplistic) review of the worldview claims of traditional cultures, modernity, and postmodernity. And when you need a worldview (and you do need one) Smith puts his money on tradition culture, if with caveats.
The current Convention makes me reflect on the old saw that Unitarian Universalism is the "Democratic Party at prayer" - which is huberis - and reinforces my gut-feeling that our fellowship might be modernity trying to make a religion for itself. Which begs (as a : to what or whom would be be praying? To the delusion of a transcendent being? After all, scientific materialism wouldn't recognize another option. (To tell you the truth, it gives me the creeps when I meet Humanists who express contentment or even joy that they 'know' they live in an impersonal universe.)
Little wonder we make jokes about prayer being optional. A joke is easier to make than a prayer, if the act of prayer brings your core assumptions into basic doubt. (Don't believe the hype that we really like doubt that much. We like options, and doubt can leverage options.) Of course, as a Christian, I have to question a spiritual relationship I have with others in the Unitarian Universalist fellowship if prayer to God cannot be included.
Back to the book: others have wisely said more than this about liberalism and its captivity to modernity, but I have a feeling that Smith's book, which came out in 2001, might offer something for those new to the discussion.