I think the heart of the empiricist objection to belief in God is that they are unable to observe anything supernatural.
But does the fact that a person is unable to observe something have any bearing on whether or not it exists? And if not, is empiricism any use at all as a metanarrative to provide guidance as to what is true and what isn't?
A blind person is unable to see things - by definition - although obviously he or she can observe things by using other senses. But does the fact that somebody is unable to see mean that he or she would be right to conclude that there is no such thing as vision?
A scientist living in the pre-modern era might have no means of detecting radio waves. Does that mean that radio waves didn't exist in the pre-modern era? (No - they are generated naturally, as are all sorts of electromagnetic waves). Does it mean that he would have been right to say that there was no such thing, as an empirical worldview might have led him to?
People who have an empiricist worldview can argue this in one of two ways. They could firstly say that from the perspective of the blind person, or the scientist, they would be right. If so, empirical truth becomes relative - something which I'm sure my commenters would thunder against! Or they can say that those people would be wrong. The fact that the blind person can't see doesn't mean that there is no such thing as vision. The fact that the pre-modern scientist can't conceive of radio waves doesn't mean that they don't exist.
What about God, or the supernatural. Does the fact that God can't be observed have any bearing on whether or not he exists?
NO!!!!!!!! Of course it doesn't. There are all sorts of reasons why God might not choose to be observed, why the universe might appear not to contain anything supernatural to a sceptical observer, why a reasonably plausible case might be made for the natural origin and evolution of the universe. But this has absolutely no bearing on the issue of whether or not there actually is a God.
Another question. What is the impact of an empiricist worldview on the pursuit of knowledge, compared to (say) a theistic one? The theist will continue to observe the universe, eyes and imagination wide open, looking for new things. The empiricist will work towards simply closing the gaps in knowledge, and not expect the unexpected.
I'm sure that this will provoke some response ...