If WhatsApp decided to move to payments, it is the closest analog.
The UI is definitely worse (IMO) and they've done a piss poor job at tying users to identities more than using phone numbers. Nobody I know uses Cash App except in exceptional cases. I have to double and triple check usernames to make sure I'm not sending money to the wrong person.
The Cash app is a pretty small percentage of Square's revenue. Square isn't much more than a credit card processor for small businesses IMO.
WeChat definitely does many of those things, but that’s far from it’s only monetization Model