My father grew up in a household of Swedish immigrants ( came over at the turn of the last century). My grandparants must have spoken Swedish in the house quite a bit because he had a pretty good grasp on the language.
We visited Sweden in the seventies and he was able to converse fairly well but all the Swedes just broke up listening to him because he was speaking, to their ears, an antique version of their langage.
The poor guy, we flew into Copenhagen. We checked into the hotel and he proudly spoke his antique Swedish (to the Danish hotel clerk). She smiled and said, “Mr. Anderson, we speak English here.
Language evolves over the course of time, with the exception of "dead" languages. For example, the Lebanese speak "lebanese" at home but learn Arabic which is the official language of their country. It's quite fascinating. When two individuals converse in "lebanese" they interject English or French words for the ones, like "ticket" or "computer" that do not exist. I encountered a similar situation while working for Air France. All correspondence exchanged with HQ had to be written in French. As automation evolved rapidly in the US, with no word for "tape drive", etc. we would insert the English word. It did not take long before the government agency that controls language, issued a document with the new French translations. "Tape drive" became "bande magnetique". One of my French coworkers visited Canada and explained that the "french" spoken at home, is what was spoken in France in the 16th century.
Latin, Koine Greek, Aramaic and many other languages are defunct. There are still a few villages in the Middle East where Aramaic is still spoken but ... other words must be substituted for those that are missing.