Ecclesiastes is not Godless. God is mentioned in Chap. 1, 2, 3, 5, 6, 7, 8, 9, 11, and 12.

This book is an accurate record of what it feels like to be an apostate - one who knew the Truth but rejected it. God warned Solomon of some specific sins he was to avoid, but Solomon rejected God's instruction and spiraled into guilt and depression. The book is meant to instruct us when we're tempted to gorge on sinful pleasures. We don't need to wonder what it's like to be a billionaire without God; we have the written record right here.