The primary aim of Bitcoin creation was to be a payment method and not a currency.
A medium of payment can be called as a currency therefore bitcoin's creation was meant to be a currency and it's just the same as payment method.
I think you are wrong, not all payment methods are currencies, for example gold, gold can be a legitimate payment method and gold remains not as a currency. One more, I have bought something in the PlayStore, I use the method of paying credit, then is the credit recognized as a currency?
Actually, if seen from Satoshi's goal, it is true, he created bitcoin to make new innovations in transactions between P2P-based users and decentralization.
Is limited supply money such as Bitcoin better over the current forms of money?
I think yes, because bitcoin is more unique than infinite fiat. The popularity of bitcoin is increasing, of course not only from the system it adopts, but from the amount of supply that is increasingly scarce, therefore many people see the potential for bitcoin, so they use it as an investment field.