Whosever is sinless needs not a redeemer, says nothing to man's ability to be sinless. Whosoever is in hell is hurting, it says nothing more than describe the results; Believers do not perish, that is the point, jew or gentile. Can dead men believe on their own?
Some hide behind this word, "Whosoever"; and I fully agree, "whosover" bears X, gains Z. However, the term says nothing about who ever can bear X. Whosoever gets pregnant gains weight, this does not indicate that men can get pregnant. So the usage in the Bible does not entail man's ability.