“The non-O movements state as a matter of official policy that they reject the Divine origin of the Torah and the mitzvos. ”
Most non-O Jews have no understanding of their religion. They are not beshita anything. They never spent much time looking into it. I would say that they are passive apikorsim.
Gadolhadorah wrote that many Conservatives know much about Judaism. I think that was true a generation or two ago. The younger generation, for the most part, doesn’t know nor care.