The biggest challenge for any crypto project is mass adoption and for various reasons many people still prefer the traditional method over blockchain technology.
They will prefer it and it will take a long long time before a transition will start.
People prefer to use the traditional method of paying which is the fiat currency because they feel comfortable with it. Another one is that is the currency that all of us are accepting unlike crypto that only a few are accepting it as of this moment. I agree that it is the biggest challenge right now and its normal too that transitioning from another currency to another will take some time.
Bitcoin is definitely the way to go, there is no way that it wouldn't be bitcoin. All we need is a way to get into phones of everyone. The shops that suppose to accept it needs to actually handle this part, if we could convince more and more places to accept bitcoin or even any other coin then we are going to be doing fine, but it hasn't been that easy at all, it has been quite the challenge.
There are tons of people who are willing to pay with crypto to buy something, and there are not enough places that take crypto for giving whatever it is, so we do not need to convince people who spend money, we need to convince people who accept it, like a cafe, an ikea like place, a bookstore, a hotel, whatever it is, just accept crypto, and we will have mass adoption for sure.