Science isn't so much atheistic as it is anti-faith. ALL statements in science can and should be challenged. All require support from observations that can be made even by non-believers. Any statement that cannot be tested is discarded as being non-scientific (even if it might be true).
If the notion of deities were testable and passed observational tests, then it could be scientific. But that has simply not been the case in practice.
If the notion of deities were testable and passed observational tests, then it could be scientific. But that has simply not been the case in practice.