The decentralised check against double-spending is bitcoin's only solution. And it's quite a genius solution, in a way. Bitcoin is not the first cryptocurrency,

The decentralised check against double-spending is bitcoin's only solution. And it's quite a genius solution, in a way. Bitcoin is not the first cryptocurrency, but it's the first decentralised one. Other than that, bitcoin behaves more like cash than like banks or credit cards. You can build banks and credit cards around bitcoin, and you should, but bitcoin itself is just like cash, and that's all it should be. It doesn't need to solve other problems that as you say have already been solved by systems like two-factor authentication and the like. This particular attack is more like thieves walking into a bank and claiming to be a person and then being able to get cash from the bank's safe (an analogy that also fits nicely with the relatively small amount of money they were able to steal). It is not like being able to rack up fraudulent charges on a credit card.