The Teacher explicitly refers to his achievements (2:4).
For the Teacher, Death is the great equalizer —it doesn’t matter if you’re rich or poor, a success or a failure.
He built and planted; he created gardens, parks, and reservoirs (2:4–6). His household consisted of many servants and livestock, and he adds that his household was greater than all before him in Jerusalem (2:7). He became exceedingly wealthy, with the treasure of kings and provinces (2:8). The Teacher is not bashful in assessing his achievements: he became great, and he overtook all his predecessors in Jerusalem (2:9).
He has achieved all that could be achieved. He has lived according to wisdom. He has become a success. But, at the end of the day, the Teacher finds all this to be futile. It is mist. It is vapor. All his achievements are fleeting.
The truth that the Teacher grapples with throughout the book of Ecclesiastes is that everything must be seen in light of one overarching reality—Death. A generation goes and a generation comes (1:4); there is no remembrance of those who lived before (1:11); all the fruit of your work will be left to another when you die (2:18); all come from dust, and all return to dust (3:21).
For the Teacher, Death is the great equalizer—it doesn’t matter if you’re rich or poor, a success or a failure. Death wipes out your achievements and makes your work irrelevant. Death renders you back to dust.
So, Ecclesiastes gives us a sober qualification to the optimism of Proverbs. We could think of them both as developing the themes of Genesis 1 and Genesis 3. In Genesis 1, God creates the world, and humans will do well if they live within the design he has set up. Proverbs draws on this to say that life according to wisdom recognizes that God is creator and we are his creatures living in his world. But Genesis 3 brings corruption through the Fall, and humanity will no longer be able to live perfectly in God’s creation. Sin and death are in the world, and work will be tough. So Ecclesiastes recognizes that death brings futility to all our activities and aspirations. There is no escaping the consequences of Genesis 3.
At least, there is no escape that the Teacher can see. Not yet.