The pronunciation changes over time are a bit of guesswork, but otherwise the video's probably right.
Pronunciation changes between different communities separated by distance are another thing. It's quite possible that the accents of modern rural New England are closer to 17th century English English than modern English English. If that makes sense. We say "Autumn" now but once upon a time said "Fall". The American colonists stuck with Fall while we adopted yet another bit of badly pronounced French to add to what centuries of being ruled by French-speaking nobles and their French hangers-on had already done to Anglo-Saxon. Then there's the Norse influence, the Hindi, Bengali and Urdu words that came from the Empire, bits and pieces from all over the place.
And even English people can have difficulty understanding other English people's accents. Not as extreme as it was before the BBC and radio perhaps, but regional/local accents still vary even over a few miles.
Where will it all end? Who knows, languages change all the time and resisting that change is a waste of time.