You have two sets of humans. One is stronger, richer, more intelligent, a bit more arrogant. They build the world. Advance technology and living conditions. The arrogance stemming from being able to do so much without any praying makes them refute the existence of God. They think everything good they have available is because they worked for it and made it happen for themselves. So obviously they have no one to be grateful to for the good things in their lives. They just want more and more. Greed fuels their soul.
Then there is the weaker, dumber people. They hardly scrape by. Work their asses off in menial jobs to have food to eat at the end of the day and somewhere to sleep, even if there are leaks in the ceiling. Their only hope is God. A being they have trust in. They trust that He will make their life better sooner or later. They are grateful for the smallest good things when they happen to them.
Now suppose God has made things so that the more you believe in Him, the more life gets harder for you to test your patience and your spirit. To test your faith. Want an easier life? Don't believe in God and the entire world becomes your oyster. With no limits to stop you, you can do everything and accomplish anything. You are limited only by your imagination. It's easier to see why these people would become the first set of humans.
So when this Universe comes to an end and there is a Day of Judgement, would these two sets of people be judged the same way? One had everything and disbelieved and even refused to acknowledge God's existence. The other had barely anything in comparison but still clung to their staunch belief in God's existence, remembering Him in everything they did, before everything they did and after everything they did. Which set of people is God going to be lenient towards? Who would be more deserving of His mercy on that Day?
Heck, I'm not even a learned theologian. I just like to dabble in a little bit of everything. Imagine the arguments presented by a real theologian. There's a reason there are whole books on the topic. And the question why make things so complicated? Well, He is God, after all. He has the final say. Us mere mortals can't even begin to argue with Him and His Will. He does what He wants and He sets the rules of the game and we have to play by His rules. Else it's Hell for us, along with Satan who disobeyed Him. That's just the way things are. Someone can choose to ignore all this and live a blissfully ignorant life full of joy and fulfillment and contentment and have nary a worry, being pleased with themselves that they did the very best with what they had. That is, until they wake up after death and find out they were very, very wrong about EVERYTHING. By then, it will be too late.