From prayers that included thanksgiving for the departed from among the early Church, to addressing those departed saints directly, there was a "subtle shift". If that were not so, then there would not be the very absence of such specific aspects included that I'm talking about.
That shift (or could it be said --addition) has long been recognized by many, and excused, justifying the development by appealing to 'the consciousness of the Church' and the like, putting it as being part of an expanding revelation.
In one sense that sort of thing could be compared to Gnosticism (secret knowledge) gone mainstream...
Which "Mass"? The Latin Mass, alone? Why even restrict search to "text of the Mass"? That's a rather artificial restriction. The little cakes set out for "Mary" and the hailing her as "Queen of Heaven" wasn't restricted to being within recitations of Liturgy, yet was deemed heretical.
You say it was due to a sacrifice being offered...and so was deemed heretical for that reason?
What of sacrifice of praise? The most ancient Church gave thanks and praise to God for having provided those whom were regarded as "departed saints", even imploring God to not forget them. Yet did so (in earliest times) without including recommendations that such persons should be prayer to directly for their own personal intercessions.
Just where is the oldest prayer specifically addressed TO Mary instead of being about her, or in thankfulness and acknowledgment for her, other saints found? Do you know?
If the remembering goes back to the 4th and 5th centuries, then you have something.
Where though, from prior, yet more ancient times (remember -- you did day that word "ancient", hence my objection here) such as in late 3rd to early 4th century is the memory of prayer to departed saints that includes addressing them specifically while requesting their own intercession?
Looking East there are traces of "veneration of Mary" gone to full-on prayer directed specifically towards Mary due to her own 'merits' (including among early Christian history's Gnostics), and some bare, isolated traces to the South sometime in the 3rd and early 4th centuries -- but in the Western Church, (for which records are best, it could be said?) earlier than about that time there is none that I know of that includes directly imploring those who would be mentioned during liturgical presentation, including among liturgy more generally what's recorded as being outside (and perhaps alongside) what has come down to more recent eras as formalized "Mass" in the Western Church, yet was still part of the overall records of what took place, and what was said during times of worship. Some liturgical presentations would go on for many hours...
Nonsense. An absence of evidence doesn't prove anything either way. You would need either a positive example of it being done (to support my side), or a specific condemnation NOT to do it (to support your side).
But we can help clear the fog of the pre-Nicene period with the following logic.
IF there was a shift in Marian prayer, and the shift went against standard practice or orthodoxy, then someone would have probably complained. But no one did. It wasn't listed in the heresies that Epiphanius collected, as the Collyridian heresy was. It was simply accepted widely and without any controversy.
Your idea that no one complained because it happened so subtly is rather strained. Nothing happens that subtly.
Just where is the oldest prayer specifically addressed TO Mary instead of being about her, or in thankfulness and acknowledgment for her, other saints found? Do you know?
The Sub Tuum Praesidium. On a papyrus dated variously from the mid-3rd to the 4th century.