Sure.
Latin is a dead language in regards to society speaking it. The language is the same now as it was 500 years ago. All other languages change through time, which is why if you try to read something from 500 years ago in English, it is quite difficult. This is why Latin is a pure language, it will not have the same changes now which happen in spoken languages. This also did occur in Latin itself when Latin was the spoken language of society, such as the dialect of vulgar Latin.
So yes the language is pure because it does not face the change other languages do. What it says 500 years ago is exactly what it says now.
It’s the same in the Greek church; they use Koine Greek, which is a dead dialect but it is pure, and for that matter exactly the language the Apostles wrote in and spoke.( The Hellensists anyways)