I'm always perfectly happy when someone calls the big bang the moment of creation. It could have been.
Not really true.
"We don't know exactly how the Cambrian explosion came about, but have a lot of good evidence on how evolution works, which allows us to probe deeper into theories about what happened" is not equivalent to "it's all random chance!"
I do not differentiate between agnostic and atheistic thought. They are both the same thinking/belief systems in my view. An agnostic believes there could be a "god/creator" (but does not pursue this thought any further than "maybe"). An agnostic also believes there may not be a God/Creator given the absence of evidence to justify such a belief. An atheist believes that there is NO god/creator given the absence of evidence to prove the existence of such a being. If evidence had to exist then the atheist will believe the existence of such a being based on such evidence. That sounds exactly the same.
As to your point about "we don't know" - well, not knowing is perfectly fine in science. We cannot ascribe to or embellish and fabricate imagined facts and agents to any unknown phenomenon without evidence.
I find it very interesting that in de US there seem to be a lot of gnostic atheists (they know for certain there is no god, and are very vocal about this), while in Europe most people would be agnostic atheists, and they don't care as much.
My impression is Biblical literalism is more widespread in the US compared to Europe, which in turn is easier to decide for or against. Especially the discussion about evolution vs religion is almost entirely absent in Europe. Framing evolution as opposed to a belief in God means it is pretty easy to become an atheist, since we have overwhelming evidence for evolution.