If you read his latest interview he goes into detail about the process of the signings that have been made, he was involved in the process, but he cannot be held fully responsible for there success or failure at United. I also think winning two trophies in two seasons, with the squad he has had, is getting a tune out of them.
I think its best to stop looking behind at what has happened before the takeover of the football side of the club, we know we were run by buffoons and we cannot change that. I am sure now we have experienced management in place above Ten Hag, things will improve over the next couple of seasons, If they don't then the manager will have to answer questions from his bosses.