The biggest issue is how God is defined. And I think this is the biggest problem. It seems that the word or the concept cannot escape from the petty and limited minds of human beings — especially religious followers and leaders who have historically used the word to represent a superior being in the sky who lords over people and offers rewards and punishments according to how they think and act. God, then, has become a tool for control, war, murder misogyny, genocide, hate, “otherism” (my term), nationalism, extreme racism, infanticide, frogs in your backyard, and so on.
On the other hand, used as a metaphor for a supreme force, God seems to make more sense (but still not to me), because it suggests there is a force greater than the limited human mind and body, which there apparently is. But it's not enough for people to call the force God and let it go. Instead they are compelled to add their litany of anthropomorphisms that add up to favoring one group over another, or ignoring some (most?) acts of terror while selecting a few to quell.
Many years ago an atheist friend told me he believes there is a supreme state of being, but not a supreme being, which seems to be a more tolerable idea than the God of the Bible or what most people are trying to shove down the throats of their fellow man, woman, child, and pet. Quoting the Bible to explain God makes as much sense as reading the Bible to understand history.
Meanwhile, people are hardly aware and able enough to vote a non-criminal, compassionate leader into office, let alone to tell everyone else what God and his message is and how they should behave. Human beings are like cats on the end of a leash, lacking the ability to be still enough for introspection into their own sense of self and the nature of reality. Instead, they are all over the place. They really need to get to this place of stillness beyond the tiny mind of the ego before espousing ideas that they’ve learned from others (even if esteemed religious figures or scientists) without any experience of their own regarding the unlimited and unconditional love of a God who remains unseen and unknown.
Just pointing to the fact that your football game won on a fluke and then thanking God for the outcome really isn’t proof that there is a God, especially if you’re the heartbroken player on the other sideline crying out to God in your pain and humiliation. And thanking God that he saved your house from a flood or fire is as arrogant and self-centered a belief as there can be, especially when your neighbors suffered a horrific loss in the same event. Religion, of course, has an answer at the ready: God has his ways, you have bad karma, God only loves one religion and its faithful followers, and God is mysterious. What’s mysterious is the inability of humans to think clearly despite that they seem to have brains inside their skulls.
Quoting scripture is about as disingenuous as a person can get on this topic, because religious scriptures were created by people and have their mark of limited thinking written all over them. When they do this they create an infinite regression of unproductive argumentation.
When a person's answer is that God does what God does then it is just an expression of not knowing but believing. But belief has no value except to warm the cockles of one's troubled and frightened spirit. But who wants to go around with warm cockles anyway?
God is a mystery because people have created the idea of God, and people are mysterious in that they are in constant conflict but unwilling to do anything about it. Unlike other creatures, human beings create ideas and then believe they are real. That is not much to hang your hat on.