@midknight you've started a bible study here. (smiling!)

Before I say my opinion on this, I would like us to look at the same scriptural text in other translations:

Ecclesiastes 6:1-2 (AMP)

here is an evil which I have seen under the sun, and it weighs heavily on men: 2 a man to whom God has given riches and wealth and honor, so that he lacks nothing of all that he desires, yet God has not given him the power or capacity to enjoy them [all those things which are gifts from God], but a stranger [in whom he has no interest succeeds him and] enjoys them. This is vanity and it is a [cause of] great distress.

Ecclesiastes 6:1-2 NLT)

There is another serious tragedy I have seen under the sun, and it weighs heavily on humanity. 2 God gives some people great wealth and honor and everything they could ever want, but then he doesn’t give them the chance to enjoy these things. They die, and someone else, even a stranger, ends up enjoying their wealth! This is meaningless—a sickening tragedy.

The scriptures you pointed out, in my understanding, is telling us in subtle terms that every man, whether Christian or non-Christian will die physically someday, somehow; and when this happens, it marks the end of one’s ability to apparently enjoy whatever materials possession he or she has been blessed with, be it money, power, gold, just to mention a few.

And importantly, it is telling us about the futility and limit of life our mortal bodies can experience. That no matter how much an individual has in his or her bank account, or the number of children he or she has, educational degrees he or she, etc., man will remain empty if he doesn’t have the hope of eternal life in and through Christ Jesus.

Hence, to the natural man, the evil thing is death!
"Vanity upon vanity, all is vanity!" Says King Solomon.

Thanks for sharing.
kind regards.