To break it down: God is completely pure (without sin). To be with God (which is what we would call 'salvation') we would also need to be without sin. Obviously, no human is without sin - meaning we could never be with God. Prior to Jesus, we were required to sacrifice things in order to atone for our sins and get right with God. Jesus provided an eternal, perfect sacrifice to pay for everyone's sins. It isn't so much that we need to worship Him, more that we need to accept the sacrifice He has already provided - if we reject the sacrifice, the full penance for all our actions is on us, and we can never be with God.