OK… let me mention (again - it was pointed out before) that The Man in the Iron Mask is a French novel, so it’s relevance to English is slight at best. French translated into English has a tendency to come off flowery or formal. For a short example:
Is literally “One speaks English here”, which really IS the way folks say “English spoken here” in casual French.
Also, French even has a verb tense that is used only (or nearly so) for written passages, which English does not do.
The point being, do not compare apples and oranges, or even des pommes and des oranges.
As for M. Villon… his French is about as close to the daily French of France as Shakespeare is to our English. It may have been common speech in his time, but it’s not something you’ll be able to read if all you’ve had is high school French in America.
As far as English goes… through the first half of the 20th Century English English was considered a “higher” form of the language than American. Thus, in cimena as well as the stage, actors would frequently adjust their English toward the English style of speaking, particularly in words like “can’t” and “again”. The Three Stooges did not - but then, they were portraying the “uncouth”.
We are in a unique circumstance in history, where we can actually hear, through recordings, how people sounded 100 or more years ago. ALL languages change over time, and more rapidly than people suppose. It’s not that English is somehow “devolving”, it’s that it’s changing. New words enter, some old words leave or change their meanings, new sentence style evolves. At one time, being able to construct elaborate, complex sentences was highly valued. Now, we value clear, direct speech. Those are two different ends And the language adapts. A hundred years from now there will be folks nostaligic for the speech of today.