The problem is not simply that you were not clear enough, though that was a problem, but that you clearly said it was patently false that “the validity of the eucharist depends on the intention of the priest during the consecration”. What ensures proper intent is another issue.
And while proper intention to confect the Eucharist is normally held as expressed by the words of consecration, yet that cannot fully assure it, therefore there is the warning against intent as in pretense, which can have the correct form in words, but in pretense, thus invalidating the sacrament.
And this is also true in sacraments as baptism, in which one can have proper matter, proper form, yet improper intent, and the proper words do not assure the minister intends to do as the church does.
It is patently false. The Intention of the Mass spoken by the priest is not the intention or intent of the priest. As one who grew up diagramming sentences the difference is not subtle. The two types of intentions are differentiated by their predicate nouns; priest and mass. That is pretty clear to me.
Peace be with you.