The loss of truth can be experienced in many and various ways. Truth is not just lost when people deny it (which is usually obvious). Truth can also be lost when it is blurred or glossed over. Another way truth can be lost is when it is reworded into oblivion. Take for example the statement: "he lied". We can obscure this truth by saying, "he chose a different way of describing what happened". You get the point. The following is an example of a problem with what has happened to the Mass.
Here is the Novus Ordo opening Collect for the Thursday after Ash Wednesday:
Prompt our actions with your inspiration, we pray, O Lord, and further them with your constant help, that all we do may always begin from you and by you be brought to completion...
Here is the Divine Worship opening Collect for the same day:
O God who art wroth with them that sin against thee, and sparest them that are penitent: we beseech thee to hear the prayers of thy people that call upon thee, that we, who have most justly deserved the scourges of thine anger, may by thy great mercy be delivered from the same...
Compare them for yourself. Clearly they are not making the same point. The first amounts to "God, please help us be good". The second amounts to "God hates sin and we deserve punishment, our only hope is to beg for mercy". Now imagine if you are fed on a constant diet of the first. It is generally nice and not offensive, but also not very challenging. Sin is not denied, but it is also not even mentioned. It just speaks politely about asking God to help.
The end result of this kind of language in the liturgy is that the faithful will have less and less concern for the gravity of sin. In the Divine Worship Mass, however, the very opposite is true. You cannot get away from the fact of sin, and the fact that it deserves a just punishment. It does not fixate on sin alone, because it also clearly expresses God's mercy. Yet, only when we truly grasp the nature of our sins, can we truly appreciate the nature of God's forgiveness and redemption.
The truth we hear in the liturgy on a regular basis impacts our spiritual growth (or lack thereof). This is not a matter of whether we are using sacred English as opposed to modern English (although that is a factor, it is not what I am speaking about here). This is merely a matter of the content of the liturgy. The question we must ask is: what does God want from us? Are we supposed to be thinking "nice thoughts" or are we supposed to be thinking the whole truth of God?