Data, being technological, shouldn't need as high-resolution as biological beings, as he doesn't have cells or DNA.
Why should we assume that?
For all we know, a positronic brain is far more intricate in structure than cells or DNA, and needs a more capable replicator set at a higher resolution.
In any case, positronic brains remain a rare technology in ST:NEM. It's not that the Federation can't build them, though: Dr. Bashir had positronics available when he tried to fix Vedek Bareil's brain. It's either that nobody has the skill or patience to do them as well as Dr. Soong did - or that nobody bothers because there aren't any worthwhile applications. Why build more Datas?