The theologically realists went to Humanism. The theologically non-realists went to theism, including creative reinterpretations of Christianity.
The fundamentalists denied modernism altogether.
The differences are less than what they seem and certainly less than what late 20th century people thought.
We are all post-modernists, in that we understand now that humans are not particular rational or consistent in their thinking. We construct our most important thoughts, about politics, romance, religion, culture and science, out of a mish-mash of actual facts, myths, stories, experience, our personal psychology, our social location, and cultural influences. We each have a powerful 'will to believe' our most basic beliefs.
Most of what we say about religion is derp, if you define "derp" as communication that repeats prior assumptions without regard to any new evidence or input. Derp is the expression of our "will to believe" or "the loyalty we feel toward our already established opinions."
When the GOP announces that what the economy needs right now is tax cuts for the wealthy. They are speaking pure derp. It wouldn't matter if the economy was booming, or in the ditch, it is what they would say.
It's OK that people have strongly held opinions. And it is a godsend that we have the internet where people can derp to their hearts' content.
Unitarian Universalism accommodates both humanism and theism. Some of our best thinkers have spent a lot of energy trying to bridge the gap. Theists try to present Christianity within the limits of Reason (a project going back to Locke). Humanists try to inject as much awe, and reverence, and wonder into their descriptions of the natural world as they can. They are usually met with torrents of derp, as people see what they are trying to do and call them out.
This is why I think for Unitarian Universalism to move forward it must set aside our treasured theological arguments and the arsenal of derp that we have at our disposal to continue them.
In a Post Modern era, theology is like art. Is any school of art: abstract impressionism, realism, expressionism, conceptual, pop, etc.; really less art than another? And do any deserve being taken as offensive?
The core of our message cannot be belief; it must be character and virtue. It does not much matter if your response to modernism is theological realism or creative reinterpretation, what Unitarian Universalism asks of you is: are you reverent, kind, truthful, giving, open, humble, and bringing all of your power to bear? Who are you?