I don't believe this at all. Social mobility definitely existed. It was at least possible to educate oneself and rise in society. Maybe the effort required wasn't equal for everybody, but it sure as hell wasn't impossible, because I've personally seen it happen.
That is fundamentally different from this supposedly K shaped economy world where it is literally impossible to rise. Education and talent don't matter anymore. It looks like the possible futures are either a post scarcity society or a cyberpunk dystopia.