Doesn't the Church claim that her teachings have never changed? Why, then, is she changing the Mass?

“Love the Lord with all your heart, and with all your soul,

and with all your MIND”--Matt 22:37

Yes, the Church's teachings have never changed.  Public revelation ended with the death of the last apostle and the Church's teachings were whole and entire by the end of the Apostolic era.  (There is, however, an entity called "development of doctrine" which is fodder for another apologetics discussion. Thus, while our understanding of a truth proclaimed by the Apostles may evolve and improve, doctrinal development is not a proclamation of a new teaching or an innovation. Please see this analogy, posted on a prior apologetics discussion here, to revisit the discussion about how doctrine may evolve.

And yes, the Church is "changing" the Mass, if by "changing" we mean offering a new, improved and more precise translation from the original Latin.  However, this is not a doctrinal change. It is disciplinary change.  Doctrine simply means "teaching" and discipline is "how we apply these teachings to our spirituality and worship".  Doctrine doesn't change (see above) but discipline can and does change.  (Another example of a disciplinary change:  abstaining from meat on Fridays.  In the pre-Vatican II days all Fridays during Lent were meat-less.  Now only on Fridays during Lent we are enjoined to abstain from meat. This was a disciplinary change, not a doctrinal one.)

So where does the Church receive her authority to make disciplinary changes?  From this weekend's Gospel:

Amen, I say to you,
whatever you bind on earth shall be bound in heaven,
and whatever you loose on earth shall be loosed in heaven.--Matt 18:18

In other words:  that which the Church enjoins upon us, heaven (that is, God) is enjoining upon us.  That which the Church permits or grants, heaven (God) is permitting.

In my opinion, one ought not dismiss lightly that which the Church proposes, saying, "Well, I don't agree with the Church on.... ".  Because, based upon the above Gospel, (as well as the words of Jesus in Luke 10:16:  "He who hears you (the Apostles and their successors) hears Me") it is the equivalent to saying, "Well, I don't agree with God on <fill in the blank.>"  Eek!

A critic may say, "Well, this gives the Church the power to say anything and claim she is speaking in God's name and people would just have to blindly follow."  This is not true.  The Church does not have the authority to change anything she wants.  For example, if the Pope suddenly were to proclaim, "The Blessed Mother is now part of the Trinity!" he would have no authority to make such a claim, for it changes the deposit of faith, given once for all, to the holy ones".--Jude 1:3.  And how do we know that a corrupt pope won't do this?  Because we are given the assurance from Jesus himself that the "gates of hell will not prevail against" His Church.--Matt 16:18.  (And we have, sadly, had some really, really bad popes in our 2000 year history of Christianity, but as a testament to the truth of Jesus' promise to protect his Church, none of these corrupt popes has ever made any doctrinal proclamations which were contrary to the deposit of faith.  How incredible is that??!!)

Finally, I heard that George Carlin once wickedly and cheekily said, (paraphrasing)  "I feel sorry for the poor guy who's in hell for eating meat on a Friday before Vatican II, and now people are feasting on meat while he's burning eternally."  In response I propose another analogy:  parents may tell their children, "It is our rule that you may not drive until you are 18."  Child #1, desperate to drive at 16 laments that he has to wait.  Child #2, same situation.  When Child #3 becomes 16 parents, with their God-given authority, say, "You know, we have assessed your maturity level and our current family needs and we are going to allow you to drive at age 16."   Who could object to the parents' right to do this?  Now, it may seem unfair to the older children who weren't allowed to drive at age 16, but the parents, in their wisdom, discerned that they were not ready. Now they are met with a different child, a different situation.  Similarly, the Church, in her wisdom, discerned that her flock needed to abstain from meat on all Fridays, and later assessed that this was not a requirement for all Fridays and changed her disciplinary requirements.

Who could fault the Church for using her God-given authority to initiate this change?

For more in-depth study visit these websites:

Article on the New Translation of the Mass
  
Catholic Bible online

Catechism of the Catholic Church online

"Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect" - 1 Peter 3:15