Mark 16:15.

Hebrews 10:25.

The Church organisation is very distinct from the church. And anything that increases their participation is in line with scripture. Both growth and attendance are important.

There's already evidence it works. And it's something that sets the church apart.

Romans 12:2 indeed.

In Antioch [Acts 11:26] people were first called Christians. They weren't the regular people of that time. But people with something that made them visibly different from the Hoi Polloi.

What really is the point of a consecration that doesn't change you? What are you being set apart from?

Lots of religions have liturgical languages which are nobody's mother tongue any more. Orthodox Judaism has Hebrew (Reform/Conservative/etc too, albeit with variably greater use of vernacular): many diaspora Jews have limited Hebrew proficiency, and even for those who speak Modern Hebrew, the liturgy is in mediaeval Hebrew, which has significant differences. And some of the prayers (including quite important ones like the Kaddish and the Kol Nidre said on Yom Kippur) are in Aramaic. Most Muslims pray in Arabic despite the fact that less than 20% speak it natively, and even for those who do, modern vernacular Arabic has diverged a lot from the classical Arabic of the Quran and the prayers. The Russian Orthodox Church prays, not in Russian, but in Church Slavonic, which is a (somewhat Russified) descendant of mediaeval Bulgarian, which comes from a different branch of the Slavic language family. The Greek Orthodox liturgy is in mediaeval Greek, not modern Greek – many Middle Eastern Greek Orthodox have Arabic as their mother tongue, and many ethnic Greeks in Anglophone countries have quite limited Greek proficiency, yet still attend services in the language. The Coptic Church still uses Coptic, a descendant of ancient Egyptian, for its liturgy. The Ethiopian Church uses Ge'ez. The Syriac Churches use Syriac/Aramaic. (And what I just said of those Eastern churches is also true of many Eastern Catholics.) Many Theravada Buddhists pray in Pali. Many Mongolian Buddhists pray in Tibetan (there are many Anglophone Buddhists who pray in Tibetan too). Many Hindus pray in Sanskrit.

Having a special language set aside for prayer, a holy tongue (Lashon Hakodesh, as many Jews call Hebrew) is something a lot of people find spiritually beneficial, across numerous unrelated religious traditions. It can give people a sense of an encounter with the deep past of their own tradition. It can make a religious community feel more unified despite being divided between different mother tongues. And most Catholics, pre-1970, thought the same thing.

It wasn't like people couldn't understand it – they followed English-Latin parallel prayer books, just like people follow English-Hebrew parallel books in many synagogues today. Globally, very many Catholics have a Romance language as their mother tongue, which is historically descended from Latin, which helps with understanding some of the words. Even though English isn't, the heavy infusion of Latin (both directly and via French) into English helps achieve some of the same thing.

I think if I'd grown up Catholic with Latin instead of the vernacular, my understanding of Latin would be a lot better. I feel like I missed out on something there.

So one definitely doesn't have to be a regular Latin Mass goer – I've never been to one in my life, I've thought about doing it but its always just been too out of my way – to wonder if the Church has lost something by throwing away so much of its linguistic heritage. Personally, I'd be quite happy with a kind of compromise in which Latin was much more heavily used but the majority of Masses were still vernacular. Which I actually think is what Vatican II intended, I think the Council's original vision was closer to majority vernacular / minority Latin, than the almost-all-vernacular / almost-no-Latin which actually evolved afterwards.

And this is a separate issue from the Tridentine liturgy – you can say the Mass of Paul VI in Latin and you can say the Tridentine Mass in English (Roman Catholics never have, but some Anglican, Eastern Orthodox and schismatic Catholic churches do it)