Atheism isn't a single word exceptional of the rest of English. You have a misunderstanding. Whether you improve on it or not is dependent on your ego, however an entire established d language will not change itself to suit a your opinion.
The term you're likely thinking of is 'non-theistic'. That is a state of being without deities; thoughts, being, existential state. I recommend you do some quick reading into morphemes, specifically -ic, -ism, -ist. You will confuse people less—especially multilingualists that have English as a second lamguage—and not make impossible statements like 'newborns are atheists'.
I'm just trying to help.