"Grant Us This Day", a short story by Nancy Kress; first published in Asimov's Science Fiction, September 1993, available at the Internet Archive; reprinted in Kress's collection Beaker's Dozen.
Here are some excerpts from the story showing how it fits the description.
The story is about a man meeting God in a diner.
When I finally found God, he was slumped at the counter in a Detroit diner, stirring his coffee. The dissolving creamer made little spiral galaxies. He had a bad sunburn. I slid onto the next stool.
The "man" who was looking for God is actually a member of the judging Committee.
In the story God is an artist, and Earth is his creation.
"Nonetheless," God said, surly now, "from the Committee's viewpoint I did everything right, so why bother me, man? I filled out the application in triplicate. I listed my previous work. I filed by the deadline. I submitted work that met your bureaucratic guidelines: neatness, originality, aptness of thought. What's more original than kangaroos? Or a hundred years' war? A hundred years for a single war! So why hassle me now?"
"Maybe," I said, looking at the fat man, who had noticed the hooker was asleep and was kicking her viciously, "you could have worked a little harder on 'neatness.'"
God is frustrated with how the work is going and wants to scrap it and start over, but the man he meets gives him an idea about how to redeem his work.
"The rules say you have a thousand years to revise, before the next round of voting. Off the record, let me say I think you should consider fairly substantial revision. The Committee liked certain aspects of your work, but the consensus was that the tone is uneven, and the whole lacks coherence."
[. . .]
"Look, son," I said, "don't take criticism so hard. Instead, use it. You're still in the running, and you've got a thousand years. Rework the more outré stuff to bring it in line with your major themes. Tone down your use of color. Make the ending a little clearer. That's all I'm suggesting. Give yourself a fighting chance."
