In addition to denouncing idolatry, one of the most frequent tasks of prophets was to critique Israel for her syncretism. A H. Mowvley points out in Guide to Old Testament Prophecy, though they may occur together, idolatry and syncretism should be seen separately. In idolatry the Israelites went after alternative gods - gods made by human hands - rather than pursuing Yahweh. In syncretism, however, Yahweh was confused with other gods, and alien practises were imported into what was supposed to be the worship of Yahweh. People were supposedly drawing near to God in worship, entering "into the presence of a divine King, with expressions of loyalty, but their wills are in no way conformed to his and what they do, they do simply in conformity with custom and habit."
God hated this syncretistic worship. As Amos notes (4.4ff.), God sees it as rebellion. Israels acts of devotion were meaningless to God because their hearts were far from Him: "I hate, I despise your religious feasts; I cannot stand your assemblies. Even though you bring me burnt offerings and grain offerings, I will not accept them. Though you bring choice fellowship offerings, I will have no regard for them." (Amos 5:21-22 NIV) Mowvley points out that God, staggeringly, considers this worship to be sinful because it purports to do one thing and does another; essentially, they are lying to God, as well as to themselves. The prophets, then, are seen time and again calling the people to serve God with humility and sincerity as they adhere to His ways.
Mark Pertuit False Prophets or Genuine Prophetic Leadership?
How much are we at risk of syncretism in our worship and liturgies? Are we offering false worship because we are really there for the cool songs lead by our favourite band? Are we offering false worship because we are really there for the holy atmosphere generated by the rituals, liturgy, incense and architecture? What is the focus of our heart? Do we need all this stuff to get to Jesus - or are we using it as a shield to shelter ourselves from the Truth?