"...yet, he must join the company of his ancestors who will never see daylight again." (Psalm 49:20) What you have quoted above is explained in verse 16 in the JPS thus: "The Lord will redeem my life from the clutches of Sheol." That's redemption of life from falling into death in battle, not from the grave. The Truth must be proved by evidences and, there has never been an evidence that one has returned from the grave; from eminent death, yes, but not from the grave.
Yes, it goes on to say that one does not have to be a fool to lay in the grave forever in the afterlife. Wisemen of all sort, Jews or non-Jews will have the grave as their home forever. According to Genesis 3:22,23, the reason why HaShem banished Adam & Eve from the Garden of Eden was to prevent them from eating of the tree of life and live forever. What you are asking me is to agree with the contradiction in the Torah that eternal grave is only for the fool while eternal life is for the wise. No one can prove that but, eternal home in the grave after death is prove by Logic and commonsense.