> in the same way that it's useful to use a dead language like Latin nowadays; it's not changing so there's sort of a bit of "equality" to it, for want of a better word.
You might think so, but reading scholastic Latin from the 1700s is radically different from reading classical Latin from the -100s. Cicero was writing in his own native language, and he used the wordings that came to him.
Isaac Newton was also, kind of, writing in his own native language. Latin was used only for the purpose of communicating with an audience; it was a channel by which you could encode English and someone else could then decode French.
But what you get by applying a set of rigid encoding rules to early modern English isn't all that similar to what you get by training an infant to speak classical Latin and then letting them express themselves in the way that feels natural to them. Scholastic Latin is much easier for the modern person to read than classical Latin is; it is essentially modern language under a thin disguise.