Honest question: Can you just use email?
If what I said sounds ridiculous, that's exactly how your email proposition sounds to people who are used to WeChat. We can argue semantics and details, like "but it isn't the same, because this and that, etc.". But, at the end of the day, if email was even close to being as convenient as WeChat for the purposes that most people use WeChat for, people would've been using email already.
Sure, the thing is, people in China didn't choose to consolidate it all in one app, their government made that choice for them.
Your examples with Twitter and FB are perfect here, because both of those services are blocked in China.