You are confusing several things.
The Vulgate is the official Bible of the Church. As such, it is spiritually and morally flawless; it is the Bible that the Holy Spirit has gifted us as the Advocate of the Church. Yet it can suffer from deficiencies in regard to textual corruptions (prior to the invention of the printing press and the Council of Trent), but also from a lack of scholarly freshness. As such the Church has a pastoral prerogative to change the editio typica of the Vulgate as is Her pleasure. So where you said, “you would say that the Catholic Church is NOT trying (and shouldn’t try) to follow the scholarly project of attempting to get as close to the original text as possible”, you are wrong.
Even prior to Divino Afflante Spiritu, the Church has desired that the Vulgate be created from the original manuscripts, while conferring with its previous editions (rather than the other way around). Most of the redaction work for the New Vulgate was actually done during the pontificate of Pope St. Pius X, at the Monastery of St. Benedict. You can go back all the way to the 4th century and see that Pope St. Siricius requested St. Jerome to make a Hebrew edition of the Psalter, though ultimately it was the Gallican edition which became the standard in the West. I know of no example in history, as Ron Conte believes was decreed at Trent, where the Church took a recent Latin manuscript as preference over an elder one.
It is only my personal, non-scholarly opinion that the LXX should take textual precedence over the MT and DSS. I completely understand the contrary position and I do not think it deeply erroneous, since ultimately the final differences are not profound enough for me to complain. The ancient apostles thought the Septuagint was good enough to quote it in their testimonies of Christ, so I certainly do not think that the discovery of the Dead Sea Scrolls is evidence that the Vulgate was way-off.
If my understanding of the issue is wrong, please cite an orthodox theologian, or a blatant quote from a Papal or Conciliar document, to demonstrate it.