The first problem ─ though I admit it took me a while to recognize it ─ is that God has no definition appropriate to a real being. That's to say, if we found a real suspect, there's no objective test that would determine whether this was God or not. Instead, God is defined in imaginary terms such as omnipotent, omniscient, infinite, eternal, perfect &c &c. There's even the apophatic school of thought, which seeks to define God solely by what God is not.
Part of that problem is that there's likewise no meaningful definition of "godness", the quality a real God would have and a real superscientist who could create universes, raise the dead &c would lack.
Another major problem is that the only way God ─ and gods ─ are known to exist is as concepts, notions, things imagined in individual brains, very usually due to acculturation rather than demonstration.
Part of this latter problem is that God never appears, never says, never does; is said to be all-wise and yet the creator of this world and all its problems; is said to be benevolent but does nothing when the child drowns in the swimming pool or Hitler sets out to exterminate the Jewish population, or Putin invades Ukraine. If this is God's plan for the world, then [he] can, as they say, stick it.
A third problem is that we haven't found a single case of a culture anywhere in the world or its forests, tundras and jungles, that lacks some or other supernatural beliefs ─ and yet there's no similarity between those beliefs. If a supernatural world existed independently of human imaginings, surely they should agree on the basics, as to what, who, why &c ... but they don't. They inherit them instead from their culture and from cultures that influence their culture.
This makes it reasonable to wonder why this happens. One proposed answer is that the human brain ─ probably with parallels in other mammalian brains ─ defends itself by constantly and instantly proposing scenarios to account for sensory input, and modifying them as further information is perceived, but always and automatically requiring an explanation. Gods (&c) may therefore be a natural byproduct of this, not least back when things like thunder and lightning, eclipses, meteors, plague, drought, good and bad luck in hunting, war, love, were otherwise unexplained ─ with the additional benefit of being able to do something about these missing explanations. Religions are of course frequently part of tribal identity, along with language, customs, stories, territory, &c, since humans are gregarious and benefit greatly from their ability to act cooperatively.