Your analogy is pretty good
The role of the financial system, like the bloodstream, is allocating resources. The problems come when the financial system has enough influence that it can misallocate resources to itself, get others to unfairly bear the risks that are supposed to be borne by the financial system, and it starts reallocating the real economy to other countries. The result of which is massive concentrations of wealth, the nation having to bear intervention costs, and an export of jobs and skills elsewhere.
The bloodstream analogy gets the misallocation, and sees the atrophying of other necessary body parts. It doesn't get at all of the dynamics, but expecting it to is pushing the analogy too far.
Cheers,
Ben
