A description of something or someone that when totally optimized is still complete crap. The expression originates from the advertising campaign for Old Milwaukee Beer: despite the beer being only barely better that drinking pond water, its slogan was "It just doesn't get any better than this!"
John:"What's up with your front yard?"
Ben: "I know, I've spent the last three weekends weeding, fertilizing, mowing, trimming . . . and it still looks like a dirt lot."
John: "Another case of Old Milwaukee Syndrome, it just doesn't get any better than this."