Personas are fine right up until they’re not. By then it’s too late. Usually, it’s right around the point that demographic data gets put in.
Designing for the function of paying without physical cash or credit card allows some mental flexibility. Differentiate the function between a millennial and a grandfather, suddenly your biases are making assumptions. Worse if you start throwing race in there.
Want to create better solutions for everyone? Listen to people, regardless of their background, and address the jobs they’re trying to get done. Derive empathy from their experience. Iterate around that.