"Jesus, Tithes, First Fruits, Circumcision and The New Covenant"

What is the "why" for Jesus going to the cross. Why did HE have to die? Yes it was for our sins but the question is why did he have to die ? Were they not already giving tithes of bulls and goats as blood offerings to atone for sins? Were they not already under a priest system that God dwelled in the Most Holy place of the Temple and the high priest went in once a year for atonement? Why did all these traditions need to change? why did Jesus have to go to the cross if this system was working? Why did God make it PARAMOUNT to change the Covenant at the Cross and why is today's church oblivious to the change? Can we worship God they we want to like Cain or must we worship in Spirit and Truth? 

 John 4:24

God is a Spirit: and they that worship him must worship him in spirit and in truth.

 Heb 8:7

For if that first covenant had been faultless, then should no place have been sought for the second.