Your comment is perhaps biased from recent history, thinking of the Lakers and Bulls "dynasties", however, the rest of NBA history would prove otherwise.
Other recent champions had all-star level PGs, for example:
Tony Parker, MVP of 2006/2007 championship and instrumental in others
Chauncy, MVP of 2003/2004 championship MVP
(I'll exclude DWade since I consider him more of a SG and also Rondo because when they won the championship he was not the allstar he is today.)
Looking deeper into NBA history, the landscape is littered with dominant PG champions, for example, the first 3 Hall of Famers and the next 3 "borderline" HOF:
Magic Johnson
Oscar Robertsons
Isiah Thomas
Dennis Johnson, 3 championships w/3 teams, one championship MVP with Seattle
Mo Cheeks
Jo Jo White (MVP in 1975/76 championship)