When Solomon the King wrote these cynical words at the end of his life, he was merely recording the final results of a human existence based on himself, his efforts, all that he had done.
When taking into account the harmony of Scriptures, however, no one can ignore that apart from God's life in us, we are dead:
"15And the LORD God took the man, and put him into the garden of Eden to dress it and to keep it. 16And the LORD God commanded the man, saying, Of every tree of the garden thou mayest freely eat: 17But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die." (Genesis 2: 15-17)
Adam and Eve disobeyed, and all of mankind died with Him. Paul explains:
"12Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned: 13(For until the law sin was in the world: but sin is not imputed when there is no law. 14Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression, who is the figure of him that was to come." (Romans :12-14)
No matter how much money, power, or prestige a man acquires for himself, he still does not have enough, because man is dead, and needs life:
"All things are full of labour; man cannot utter it: the eye is not satisfied with seeing, nor the ear filled with hearing." (Ecclesiastes 1: 8)
Why does this happen for us, though? John gave the reason, and thus the antidote:
"15Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him. 16For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world. 17And the world passeth away, and the lust thereof: but he that doeth the will of God abideth for ever." (1 John 2: 15-17)
We need to know the love of the Father, and this love is revealed to us in that God did indeed do something new!
"Behold, I will do a new thing; now it shall spring forth; shall ye not know it? I will even make a way in the wilderness, and rivers in the desert." (Isaiah 43: 19)
"A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh." (Ezekiel 36: 26)
"Behold ye among the heathen, and regard, and wonder marvellously: for I will work a work in your days, which ye will not believe, though it be told you." (Habakkuk 1: 5)
What is this new thing this new spirit, this new work? The Gospel, that through Jesus we are justified from all things in which the law could never justify us (Acts 13: 38-39)
Paul even quotes Habakkuk, who prophesied that the Jews would not believe this "new thing", i.e. the Gospel. justification by faith, and the New Covenant.
When Jesus died on the Cross, He enacted a New Covenant for man:
"10For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people:
11And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest.
12For I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more." (Hebrews 8: 10-12)
In Christ, we all become new creations, too!
"Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new." (2 Corinthians 5:17)
"For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him." (2 Corinthians 5: 21)
Solomon, in his fleshly self, reasoned that there was nothing new under the sun. In Christ, we have the New Covenant, and we are made new creations in Christ. Indeed, there is plenty new for those who believe on Jesus!