Bitcoin is a long way from becoming a currency you can live your life in. You also only have 7 transactions a second. But that doesn't mean Bitcoin isn't immensely valuable as a medium-term and long-term store of value
Honestly it is true that bitcoin cannot replace currency in the world because price is not stable just like the exchanges money to other country. I believe that eventhough bitcoin price is not stable it would not be a currency in the world.