No, the only thing English HAS done since Shakespeare is to change......You are correct. If we somehow, were transported back four hundred, three hundred, two hundred years ago we would be unable to understand the language.
The Prince of Darkness is a Gentleman. King Lear
I don't think that most literate people would have all that much of a problem until the early 1600's as far as speech. The King James Bible worked to standardize and unify the language. Prior to that, regional usage and dialects might be a problem, or might not be. Certainly written English is understandable to an extent back to Chaucer's era, albeit with a bit of struggle.