Fractional reserve is just a particular kind of regulation placed on banks' creation of debt, and it usually isn't the most important one. The practical limit of banks is that they have to be able to extinguish their debts (which we call withdrawal), including being able to transfer them to other banks in exchange for cash (which we call clearing), at the whim of the creditors (you and me).
The problems with banks are the problems with debt generally, but that's much trickier than some glib remarks about monetary policy.