Disagree on that. Pierce was an ok passer and Ray wasn't much better except for a few years in Seattle. Young Tatum and Brown weren't facilitators, but they are now, and it's the main reason the team is so much better, mostly Tatum. Tatum averaged almost 5 assists this year and 6.3 in the playoffs.
I'd rank them Tatum, Ray, Pierce, Brown. A lot of it is roles though. Much of the time, Ray and Pierce were expected to score if they touched the ball at all. It was the true PG era. Ray averaged 2.7 assists in the playoffs in 2008.