Maybe that is one reason why modern and traditional payment can't replace each other. Because people itself is different, not only depends on age but not all people maybe can access mobile phone or anything like that so they still can do payment with fiat. I think it is no matter it is digital or traditional payment, but currency still currency. People use it as payment and they can buy something with it no matter who are them.
Correct, if a technology like Bitcoin becomes the new standard and people would have reason to participate in it but can't, that's also kind of exclusive, which Bitcoin is not supposed to be. I don't know though how critical the situation is when it comes to mobile phone distribution. I guess most people have access to mobile phones? I have no idea about those statistics but that might be one of the smaller problems to solve.
Modern and traditional payment can help each other as we have already seen that many online payment systems from the third party help people send their money via their bank to the third party account.
From that, those third parties can send the money to the services people want and it is already changing the payment system.
To see bitcoin become the new standard will need more time as bitcoin is a new thing and it requires approval from the government to use bitcoin as an alternative payment system.
Maybe people who can adapt to the new system will use it because they think that the new system will be more user-friendly than traditional payment, making them feel too long to see the process will finish the transaction.