Your priori is wrong. Evolution is irrelevant to your argument, based on your assumption that God is a myth.
I am not an atheist in order to justify 'sinning' I try to live an honorable life. I am an atheist because of my pursuit of truth.
“I am an atheist because of my pursuit of truth.”
And you’re idea that there is no God and nothing worth serving, is misguided at best. If you are truly pursuing the truth you will eventually come to a different conclusion.
The world has always had people who were certain there was no God yet vigorously pursued the truth. One thing I’m certain of is that there is nothing more true than God. I can only take you at your word that you pursue the truth... look forward to you joining the family.