Really? Think of any question upon which we once had a scientific answer, however inadequate, but for which now the best answer is a religious one.
Also, we are working with different definitions of gods here. Sagan is talking about deistic god, which I spent some time addressing above. But when it comes to theistic gods (the ones that care about you, that break natural laws for their people, the ones that care what you eat and on what days, who you may sleep with and in what position, ones that give themselves body so they may kill it to save their people, who take "our" side in the war etc), then we have plenty of scientific evidence these things are man made.
Besides it's really not up to me to provide evidence against some god. People who invoke him should. It's the classical celestial teapot argument. If I claim there is a tea pot circling Mars, why should you spent time and energy proving there isn't such a thing. I should provide evidence there is one.
If science has nothing to say about something what else does? Ramblings of religious people who just make stuff up and never provide any evidence for their claims? And which ones? Scientologists? Mormons? Muslims? Which one of these you will adhere to is highly correlated with where you were born and has nothing to do with the truthfulness of the particular religion. Sometimes these teach completely opposite things about god at the threat of hellfire and infinite torture. They can't all be true, but they can all be wrong.
And how do the religious know what lies beyond? Of course it comes down to "revealed" knowledge. God himself spoke to some people and told them things. And others are required to trust these people for their extraordinary claims without any evidence? Let alone the extraordinary evidence required to actually verify their claims.
And isn't it incredibly stupid of a supreme, intelligent, omnipotent, omnipresent being to demand belief in him without evidence? God would presumably know that people would invent scientific method as the only sure way to discover truth. Yet he leaves such important things as if you will be damned for eternity to belief without evidence leading to three desert dogmas that teach completely opposite things about him. Yahweh himself besides being stupid is rather evil god. Look how he behaves exactly as you would expect the people of that age that invented him to behave (he orders genocide of neighboring tribes that worship other gods, enslavement of women and children etc, just read random book of old testament). By the way he was never meant to be god of all, he was meant to be a god of a single tribe (otherwise a lot of stuff god says and orders makes no sense). Evolution of competing religions and the fact we have multiple religions like this is exactly what you would expect to see if religion were man made.
All metaphysical claims and especially all physical claims made by religion were proved to be wrong. And would you expect it any other way really. Religion was our first approximation of cosmology, medicine etc. But like all first approximations it proved to be completely wrong. Jesus casts out demons to heal people, he heals lepers instead of healing leprosy, no germs ever mentioned in the Bible (naturally no germ theory of disease either).
But now we know better. We know how solar systems are formed, we know how planets are formed, we know how life evolves, we even know how a universe can come from nothing. We really don't need god to kick off any of these things any more. Over the millennia people believed in all kinds of gods from Zeus to Athena to Thor. You are perfectly capable of dismissing them all as laughable, so you know what it is like to not believe in any of those as nonsense. Atheists just go one god further.