Latin, of itself, isn’t used as a vernacular language, so its meaning is set, a bit like ancient arabic or ancient Hebrew. The meaning of the words doesn’t change over time so there is no need to adapt them.
When mass is said in Latin throughout the world, a Catholic can go to mass anywhere and understand and be familiar with the liturgy, and know that literally those same prayers are being offered all over the world and also feel assured that those prayers are literally in communion with saints, martyrs and Catholic faithul through time.
It makes the church whole.
With vernacular you can find the balkanization of mass, sometimes within the same parish, particularly with people moving around more in cosmopolitan areas. Spanish speakers at one mass, English at another, perhaps French at another. When Latin is available, anybody can go anywhere. If they need a translation, all they need is a single hand missal of their choice.
Latin isn’t a hard language (at least the stems
) particularly if you speak French, Spanish, Italian or even English. There are lots of German words, and a bit of Celtic, in English, but mostly it comes from Latin through French. There aren’t that many words in the Ordinary of the mass said every week. Most of them are quite familiar, often from everyday words and phrases.
Problem is that Latin has become a bit of a oddity, an unfamiliar novelty, and to further confusion, the Novus Ordo in Latin is different again from the Traditional Latin Mass.