I’m a freelance writer and you are so right in saying that spoken English now becoming rather bad.
I think ‘off of’ is an American thing, as is ‘gotten. I’ve also noticed that certain words that shouldn’t be joined together now are (e.g. ‘any more’ is now regularly appearing as ‘anymore’, when these mean two different things) and that punctuation, or should I say lack of it, has gone by the wayside. With people our age, we tend to see so many mistakes in written English, that we eventually can’t remember how it should be.
I place one example of lack of a short sentence here how it could actually mean something quite different with the addition a comma:-
I have failed my friend.
I have failed, my friend.
Oh the joys ….. but isn’t it lovely to have a good command of our own native language? I know I am proud of it.