Most evidence suggest it was sincere. That it was one of the most major policy failings of the West is now admitted, even by its architects. That sort of remorse isn't common with conspiracies.
It really hasn't. China is still far wealthier and more economically developed today than it was under Mao-era policies, and for a vast majority of average Chinese this is ultimately what matters most. They have little reason to care about abstract ideals like elections or individual rights when other things are so much more relevant to them.
Just because someone's wrong, doesn't mean they're evil. The USSR had literally just liberalized after similar policies. You telling me that wouldn't have been compelling evidence 30 years ago?
I'm not even sure it's fair to say the fall of the USSR was entirely due to external influence, I do think the pressure the west put was a factor but I think internal events like chernoybyl and the quirks of the leadership sucession in the 80s had as much to do with it.
That generation is passing away, and their ability to control global geopolitics is passing away too. It remains to be seen if the whole world will ever be 'liberal' or 'democratic' and it sure seems like much of the world would rather opt out.