Totally agree, I'd even put it higher than 90%.

I spend a lot of time in Shenzhen, basically every other month. I do have a bank account with WeChat attached and only in the past year have I embraced using WeChat pay everywhere. Before that, I was almost exclusively cash. I still whip out cash on occasion without any issue. The only issue I've had with cash in the past is not having small bills for the taxi drivers. The ATMs give out 100RMB notes and the taxi drivers hate breaking them. If that's all you have they will. Small vendors on the street would prefer WeChat pay, but they still don't want to lose a sale. I've never had them refuse cash. I've paid many restaurants with cash, some of the better restaurants will even take a US Visa card. Sometimes the staff doesn't even know that that their card reader will take it, I usually ask them to try and it works pretty often. I like trying to use a US credit card as it means less cash I need to withdraw from the ATM to replenish the RMB in my bank account or pocket.

Maybe my experience is a little outdated as I've largely switched to using WeChat pay these days.

I've seen some casual restaurants moving to a WeChat only system for ordering and I assume payment. Need to scan a QR code to open some WeChat app to order your food. I don't like those systems as they are usually Chinese only and my WeChat is sometimes flaky with these apps maybe because I have a foreign WeChat account.

I'm kind of an old fart, so I don't really see using WeChat pay or any other pay systems (ApplePay, etc.) as being necessarily faster than cash. It takes a bit of time to get the QR code up, in my estimation roughly the same amount of time for me to whip a few notes out of my pocket. Experienced cashiers can make change very fast. Maybe contactless payment is faster than having to raise a QR code but I haven't tried it yet. Like I said, I'm an old fart who always carries around enough cash for a just in case situation.