"Men will flee... from dread of the Lord, and the splendor of his Majesty, when he rises to shake the earth." Isaiah 2:19.
God is not to be trifled with. I trifle with him all the time.
The difference between God as I imagine him, and God as he is revealed in the Bible, is often vast. And the token worship I offer the safe, comfortable "god" in my head, is every inch idolatry. Worshiping a tame god I've made up is as much idol worship as sacrificing to Baal was, as idolizing sex is. And much, much harder to eradicate, because it's sneakier.
Unless I am worshiping the real God, apart from my conceptions and misconceptions of him, it is idol worship.
All worship, all communion with God needs to begin with us praying "Not to what I think thou art, but to what thou knowest thyself to be." (C.S.Lewis)