You are right that the party became notably less insane when Deng Xiaoping took over. However the various administrations since then have spent significant resources and time going in different (and sometime opposite) directions, and not always in a blunder-safe way. The example I have in mind is the declaration last month by the foreign affairs ministry that the Hong Kong "Joint Declaration" is not binding any more for China. They rolled that back a week later (probably after they realized where that was going), but essentially for a few days their official stance was "we don't respect treaties we have signed, even the ones we pretty much wrote and that gave us what we wanted. Our word as a government has no value". Kind of a risky move, and could have set a precedent.

As for your specific point regarding teaching English, I think you're right they wouldn't do that now, however it's a bet I could see them make if their domestic economy becomes slightly larger. After all there are other countries (Japan, Russia, France...) where English has a low penetration rate, and they get away with it.