The opposite of this cute neologism may be Einfaeltigkeit. Not a neologism. It includes at least a little part of Einsamkeit, which is the opposite of Zweisamkeit. And Ideesamkeit at least alludes to Gemeinsamkeit. -samkeit always has to do with togetherness. But Einfaelltigkeit also means dumbness, or non creativity. It also might have to do with einfallen to have an idea. But only one in this word. But Einfaeltigkeit also is connected to onedimensional thinking. The act of being unable to think outside the box. Or outside the bun.(We love Tacobell don't we?)
Yeah, it's a cool word. A German word. Like Gemuetlichkeit :) No English aquivalent.