It doesn't solve it at all, I am talking about real money you can spend in a store, not tokens that need to be converted through an exchange into cash each time.
There are stores where you can pay with cryptocurrencies. That said, GP said "almost". We will see if it ever reaches the point where this word will not be needed.
The reason why you can't spend it at the store is because the store doesn't accept it. The reason why the store doesn't accept it is because of the aforementioned scaling and complexity issues.