That doesn't mean that said Being doesn't exist or that they mythos' descriptions of that Entity are false. Myths can be true ("mythical" CAN mean untrue or imaginary, but it doesn't HAVE to).

For me, atheism is the only conclusion I "take seriously," in that it's my belief, but matters which can only be decided (after a fashion) by faith should avoid dismissing alternative arguments out of hand. The proposition "God exists" is almost certainly unfalsifiable, at least for most extant definitions of "God."