The result of all Solomon has to say in Ecclesiastes is this: obey God. Listen to him. This is the purpose of mankind. Time and gladness and uncertainty are all contexts to invite us to intimacy with God.
It takes a great deal of respect to fear someone in the way Solomon suggests here. Our compulsion to understand is never going to go away. It is transcendent. No matter how much progress we make, we will never be fully satisfied with the answers to our questions and the scope of our comprehension. How humbling to approach The One who does have the answers. How terrifying. What are the answers He has decided on and why? What part will I play in His plans? What will I do if He hides His approval from me because of my destructive behavior?
Even when a child knows they are wrong, they fear the consequences of their parent. Like Adam and Eve, we are ashamed.
But the point of our limitations is not to shame us but to exalt God. And by doing so, exalting who we are in His Image. It is scary how much the whole thing depends on Him, how little control we have. How much His voice beckons us to obedience, to belonging. How much we need Him.
But this is the reality of the world. This is the truth. Life is an intricate design to invite us into relationship with God.