Darwin didn't invent evolution or atheism. I'm sure there were atheists before Darwin, but here I think Dawkins and Gould explain it best:
"...although atheism might have been logically tenable before Darwin, Darwin made it possible to be an intellectually fulfilled atheist." Dawkins R. "The Blind Watchmaker," [1986], Penguin: London, 1991, reprint, p.6).
"Before Darwin, we thought that a benevolent God had created us." "So Cleverly Kind an Animal," in "Ever Since Darwin: Reflections in Natural History," [1978], Penguin: London UK, 1991, reprint, p.267).
Does anyone here disagree with the proposition that the idea that the universe is not designed is tantamount to atheism?
Cordially,
No. You obviously haven't explored all the options. For instance, the universe could have popped into existence (via one of the currently proposed theories) and God could have stumbled across it later.