I think it's difficult to make friends in China mainly due to language barrier, culture barrier and different upbringings. The real genuine Chinese friends I have now and have known for a long time, where former co-workers of mine or people I met while playing sports.
The common interests are the big part of getting over the language & culture barrier. The other expats I've met, when they have Chinese friends, they seem to have always met while working together or met because of common interests like music, arts, fitness, or language exchange.
Apart from that, sometimes the friendships don't last long because the foreigners here simply don't stay for a long time, go home and lose touch after they stop using Wechat. On another note, some Chinese people are out to only practice English and not trying to build a strong connection.
Unfortunately, most Chinese can't use Facebook or Whatsapp, so If you don't use wechat then will lose touch.😥 Maybe we want to build a strong connection, but sometimes we can't do.😫
That's understood. Once foreigners go back home, Wechat becomes somewhat irrelevant. The longer away from China the lesser it's used. Although when I went back to America I still managed to chat regularly with my Chinese friends on Wechat.