So your simple mind seeing everything black and white, cannot envision that there are infinite versions of deity and faith. You're attacking a straw man, "atheism", but that's not atheism at all, just everything that's not your own doctrine, to then falsely claim that if one doesn't fully embrace your particular nonsense, their life is supposedly worth nothing. It's a segregation argument for those who already are your victims: outsiders see the game. In fact, someone who's not your prisoner is more likely to succeed in life, including the pursuit of art.
When people no longer believe in God, they will believe in anything
Apparently a similar quote was attributed to apologist and author Lewis. This is best explained as psychological projection. History shows that superstition leads to any belief and can be used to justify crimes or can lead to one's own demise. Someone who doesn't believe because of critical thinking and the lack of evidence, is unlikely to believe in other things lacking evidence. This is a false claim and a slippery slope argument.
Then if they accept knowledge like discoveries about our origins, it is because the evidence is overwhelming, it's actually what led to those conclusions. Science, unlike religion, doesn't start with an a-priori doctrine to then attempt to validate it with confirmation bias. The method actually attempts to deal with common human fallacies and to reach conclusions based on observations instead. When the model (i.e. scientific theory) is shown to be erroneous, it is improved. Then that's not atheism, it's the universal scientific method and methodological naturalism. Scientists are people with their own beliefs. A scientific consensus should be able to be independent of individual beliefs and preferences, it's about facts, not belief, faith, death denial fantasy or control ideology.
Because science has been incredibly successful and that many scientists have had a rich life studying fascinating things, your fatalist argument is defeated by facts.
Atheism has never given anyone piece of mind
It's true that they don't eat brains. I used to fear demons and the destruction of the world by a demiurge. My anxieties are better managed without those false beliefs and superstitions today.