The direction of whatsapp was really really biased and strong towards being as simple as possible and useful as a messaging medium. It worked out pretty well fwiw. Who uses wechat besides Chinese people?
Did you really ask "who uses Wechat besides 1.4 billion people" in a model that can be monetised and extremely profitable compared to a simple messaging app?
Wechat is very profitable because users use it for everything, banking, payments, ecc.
The average WhatsApp user is worth nothing in comparison even with almost twice the user base. Last time I gave WhatsApp money was the 50 cent yearly subscription when it was still an independent product.
If something has potential, it's the one that has made billions out of that potential. Unless you think that the Chinese market doesn't matter, only the Western market does.