Is the Belief That We’re All Broken and Need a Savior a Sad Way to View Life?

Questions about how to respond to an unbeliever who says the belief that we’re all broken is a sad way to view life, how to reconcile Zechariah and Elizabeth being blameless with Jesus being the only sinless man, and whether the psalms about delighting in God’s Law are outdated and legalistic.   What’s the best way to respond to an unbeliever who says the belief that we’re all broken and need a Savior is a very sad way to view life? If Zechariah and Elizabeth were righteous and observed all the the Lord’s commands blamelessly (per Luke 1), how can we say Jesus was the only sinless man? Is all the talk in the Psalms about delighting in God’s Law and meditating on it and doing things to help you follow it better outdated and legalistic?