I don't think it's true that you can't change how bitcoin works. I'm no expert, but as I understand it, if more than half the network agrees with you, you can change it.
I think the main problem with bitcoin is that it doesn't scale, because every transaction has to be approved by the entire network. More payments and a bigger network means the number of validations goes up quadratically.
I think the main problem with bitcoin is that it doesn't scale, because every transaction has to be approved by the entire network. More payments and a bigger network means the number of validations goes up quadratically.