Lots of the platforms you mentioned aren't censored because of the ability to exchange ideas, but because the Chinese government owns a Chinese version and can get more money by forcing everyone to use theirs. Like with Steam recently. State owned companies are gearing up to release their own widely released games platform next year.

No Facebook or Twitter forces people to use Weibo and Wechat. Same with Skype. Some of these companies refused to give date to the government, but the thing that decided it would be blocked was the rise of Tencent.

Whatspp is more confusing. They refused to allow the government to see the encrypted messages, but messages still get through regardless. IT just became really slow.