Your pastor is full of it. There is no other way to say it. I'm not sure what the best way is to refute this nonsense.
The Eucharist is the sacrifice of Christ on the Cross and has infinite value. Consequently, the Mass (or the Divine Liturgy) is the most powerful prayer we have, far more powerful than any individual's prayer outside that context, because it is united with the Cross. The value comes, not from being public, not from being on a prayer chain, not even, surprisingly enough, from being in the bulletin, but from the life-giving ultimate sacrifice of God the Son on the Cross applied to our requests.
This prayer is so important that in some situations where, for example, "Masses" have been offered with invalid matter, (such as gluten-free hosts), the churches or monasteries were instructed by the Holy See to re-offer each and every Mass intention with valid matter. (This is why they are logged).
- If this is true, why does it "not make a difference" whether you do it or not?
- Why, indeed, offer Masses in the first place?
- What purpose does he think it serves?
In any case, you are right, and he is wrong