Gods are man's explanation for forces. If a rock rolls down the hill - what caused it? Something must have caused it, because inertia determines that the rock would otherwise stay put. Something with a will must have decided to move it, and something with the strength must have moved it. Hence - a god, a spirit, a numen...whatever.
By the Late Republic, the Romans no longer really, deep in their hearts, believed in gods, and considered human sacrifice an abomination. They did however traditionally 'execute' enemy leaders at the traditional site...in the Temple of Jupiter Optimus Maximus Capitolinus, the national god of Rome.
We, however, are not nearly so superstitious. For example, we no longer believe in the god Mercury, the god of commerce and all that is associated with commerce, such as the spread of news (hence his function as the messenger of Jupiter). We believe instead in the Invisible Hand.
And neither do we believe in human sacrifice. Our Northern European ancestors used to sacrifice victims, usually criminals, to the gods, with hanging the preferred method. We, however, reserve hanging for the 'execution' of 'criminals'. Who are we sacrificing them to? The goddess Justice?