For instance, they may insist that God must comply with Aristotlean Laws of Logic. They might say, by reason of the Law of the Excluded Middle, commandments or revelations in Scripture must be either/or and never both.
As another example, they may insist that God must abide by their own sense of an arrow of time and thus cannot judge a person before he comes into existence to say or do anything whereby he would be judged.
By anthropomorphizing God, they deny God who IS and create a smaller "god" of their own imagining, one they can comprehend.
It's also possible (and common) to err in the opposite direction: To over (or too exclusively) emphasize God's transcendence at the expense of his immanence in the world.
For instance if God is truly immanent in the world, then some aspects of God do exist within "the arrow of time". (Some, and of course not all, which would be pantheism as opposed to theism.)
Likewise if God is ALL knowing then he must know, in some genuine fashion, of phenomena such as discovering and experiencing new things. Therefore God must have aspects of or within himself that are NOT omniscient, if God in His completeness is omniscient.
Of course both of these aspects, among others, are found in God's incarnation as Christ.
Anyway this opposite error makes for a "big" God, but also one far too distant from his creation.