Tcoat
This sounds more like a procedural issue than "boy everybody but me is dumb these days" thing. If their policy says they can't take cash that they can't put away then they can't do it no matter how much the customer would like them to.
If they do indeed have a policy like that, it's still dumb. Never, ever turn away a customer who wants to give you money. And however dumb a policy it is, it's a dumb manager who is so bound by the policy handbook that he doesn't see the stupidity of the decision. In a case like this, customer service at a fast food restaurant, good customer service is to give the customer his meal, take his money, whatever the state of the system, and take care of it later.
I had an experience when I had to buy a new truck in 2020, that illustrated a poor grasp of customer service.
My old 2002 Ranger died; the transmission was shot, it wasn't worth the couple thousand dollars to repair or replace it. So I was looking for a new truck. I decided on a Honda Ridgeline, and I contacted the local dealership, about 8 miles away.
I called and talked to a young salesman, probably starting out, maybe not yet 21. I explained that I very interested in coming in for a test drive and probably would buy the one they had on the lot. But I had no transportation to get to the dealership, so would they be able to send their shuttle out to pick me up?
The young man said he wasn't sure, he had to check with his manager. He came back on the phone and said his manager said, no, they couldn't do that, because I wasn't a customer. I told him, thanks, but that's too bad.
Meanwhile, I got contacted by a Honda dealership 20 miles away, and in another state. I explained my situation to them, and the salesman said, "I'll bring it out to you." Which he did. I test-drove it, and bought it on the spot.
The first dealership made a mistake. I might have been a customer, but they guaranteed that I would not become their customer. Meanwhile, the second dealership went the distance-literally-and gained a dedicated customer.
And I say this as someone who has spent his 30+ years in the workforce in customer service in one form or another, starting as a teller in a small community bank. The first dealership did not have a good understanding of customer service. The second one did.