The point is that it is not the same Mass that has been said since at least the time of St. Gregory the Great. It is a different Mass. Every single prayer is different; either it was changed entirely, dropped outright, or mangled in the ICEL translation. BTW, the translations in other European languages are just as bad. It's not a problem specific to the ICEL.
So there has been one Roman Catholic Mass for almost 2,000 years. Now we have a so-called New Mass. They are not the same Mass. And the words that were changed include the words of consecration.
Last time I checked "pro multis" still meant "pro multis."
SD
You forgot the free-wheeling priests who sort of make it up as they go along, improvising no doubt for the sake of "spontaneity."