Instead of "God exists as a personal being" versus "God is made up," you're saying "the referent is real, but misidentified." The biblical writers were pointing at something genuinely there—they just understood it through anthropomorphic categories rather than scientific ones.
If God is infinite, eternal, and transcendent—completely "other" than creation—how can finite humans comprehend or relate to such a being? Anthropomorphization serves as a necessary bridge between the incomprehensible and the knowable.