This is a strikingly ahistorical and cynical (not to say paranoid) take on the motives for the Latin Mass.
For the first 1000 years,there really weren't any written national languages, no English, French, or even Italian as we know them today. In the West, to be literate was to read Latin; in the East, Greek; and Aramaic, Ge'ez and Arabic in the surviving churches in the lands subsumed under the rule of Islam.
The great advantage of Latin was its inclusiveness: people could share the greatest of literature and correspond and converse in the same language from Prague to Cadiz and from Oslo to Gibraltar. (This applied not only to Liturgy, but to Philosophy, Literature, History, Mathematics, Astronomy, Medicine --- a continent-wide community of people who could travel everywhere and be understood. There's a kind of Pentecost for you.)
Most European mother-tongues had no written form, not even an alphabet, for centuries. (For instance: Dante is considered the first writer in vernacular Tuscan, later Italian: -- this is 14th century, which is early Renaissance.) Books, being either hand-written or printed by woodblock, were extremely costly to produce, and it would have been physically and culturally impossible to accommodate people's mother-tongues,
Rusyn
Polish
Ukrainian
Serbo-Croatian
Czech
Bulgarian
Slovak
Belarusian
Slovene
Macedonian
Lower Sorbian
Upper Sorbian
Kashubian
Bosnian
Croatian
Montenegrin
Serbian
Most of the above had to make do with Old Church Slavonic as their liturgical language--- not their mother tongue,
French, a dozen dialects
Italian, a dozen dialects,
Spanish, a dozen dialects,
...including Mozarabic, which was a liturgical language
Romanian
Portuguese
Sicilian
Catalan
Galician
Basque
Sardinian
Cretan
Cypriot
Maltese
Corsican
Tuscan
Dalmatian
Lombard
the Rhaeto-Romance languages
the Gallo-Italic languages
the Occitano-Romance languages
Occitan
Catalan
Aragonese
Astur-Leonese
Galician-Portuguese
Castilian
I'm not even 1/4 of the way through and I'm exhausted. I haven't even mentioned the many dialects of German, the language of the Angles, the language of the Saxons, the six major divisions of Celtic, all of which would have been incomprehensible even to a middle-English speaker like Geoffrey Chaucer (like Dante, 14th century).
Bottom line, if you're still with me: Latin was the only way people could write, be published, and communicate beyond their own, oh, Manx or Frisian or Aragonese-speaking valley or village.
And a surprising number of people DID speak Latin, especially anybody (missionaries, traders, for instance) who had any occasion to venture from their childhood hearth and home.
St. Patrick, born in Roman Britain, educated in Auxerre,France, preached in Ireland in several Goidelic (Gaelic) languages, but wrote to the pagan Franks --- his Letter to the soldiers of Coroticus (Latin: Epistola) --- in Latin. Why? Because the Franks were priests? (No.) Because Latin was the international language. It was what pagan Frankish soldiers spoke.
But that's a topic for later. Suppertime!
It is clear that God intended the apostles to spread the gospel in native languages. The message of Pentecost. The required latin mass came 160 years later.
I agree with most of the benefits you list, but to say it was beneficial to the majority of people who were poor and uneducated is a fantasy. Until the printing press and universal education people were much easier to hold down and control as they are now.