Very few things are subject to proof. In fact I can think of only a handful outside the field of mathematics. So how can you say something does or does not exist if there is no proof, or a proof is unavailable with current knowledge? We make approximations based on whatever we do have. There is no absolute metaphysical proof that other people exist, yet they are a constant part of our experience and we know of no inconsistencies in our theory of humans, so we assume that they probably exist.
There is no absolute proof that the Earth was once in the depths of an ice age, but we are certain that it once happened because of the evidence left behind. We can see what types of animals lived in which regions in which time period, and infer the climate they would have lived in. We can measure gas saturations in polar ice cores. We can see the scars on the landscape carved out by old glaciers, and infer that the region was once covered in ice.
There is no absolute proof that there are (or aren’t) gods, but we have no evidence of any where near the strength we require to believe other things. For some reason theists like to say they believe in god(s) because “I can feel his presence”, or “he has helped me in the past”. Both of these are unfalisifiable, and so are merely speculation as to what caused whatever benefit was gained by that person. As well as this distinct lack of evidence, god hypotheses tend to be so fantastic and unlike anything else we know that we cannot even judge them to be potentially consistent with reality.
However there had to be a source of the idea of deities, and we must account for this. Either gods made humans, humans made gods, or humans and gods arose independently and then discovered each other. Evolution and abiogenesis, while not inconsistent with the influence of gods, do not require the intervention of deities to be successful processes. Without evidence to the contrary, the probability of gods’ intervention is minute, simply because it isn’t necessary. Humans and gods may well have arisen independently, but that would make any right to rule merely an expression of “might is right”, and strip the gods of the sovereign right they are supposed to have to demand our unquestioning obedience. That leaves the final option, that humans created gods. Gods typically involve many human attributes, such as jealousy, hate, megalomania, libido, and sometimes love and justice. On average, gods seem to be neither benevolent or worthy of respect though, and each god seems to reflect the cultural ideals of the civilisation in which they were worshipped. This means that the most likely explanation of gods is that they were created by humans, although the reasons for this are debatable.
So to assert something does or does not exist in the absence of compelling evidence or proof, we need an estimation of probabilities considering the evidence we do have. It is an effective processes in most spheres, but for some reason some people seem to think religion is exempt from such analysis. I disagree.