The Tabula Peutingeriana is not the "best" Roman map. It's the only map of known (late) antiquity to survive, and only through medieval copies. The Tabula Peutingeriana is an itinerary map, essentially it is designed to show roads, distances, and travel networks, not to show an accurate view of the land--for distances it's quite precise. Taking the Tabula Peutingeriana as representative of Roman maps would be like assuming that all modern maps look like subway maps. No complete maps survive, but significant fragments of, e.g., the Forma Urbis are known and show quite precise distances, measures, and forms

Moreover, what precisely prevents a state from having aesthetically pleasing borders (whatever that means exactly, and leaving aside the question of the concept of borders in Roman antiquity) without having nice maps? There were states even in the Middle Ages that didn't know how to make good--or any, if they were illiterate societies like the Mongols--maps which, you could argue, had perfectly fine borders (a decidedly subjective measure)