Can we just put this inferior lens thing in to context...
In the MF World there is Zeiss, and then there is everything else.
To say Bronica glass is inferior by a small degree is kinda true, but then so is everything else, and the likely hood of your average joe being in a position where they would tell the difference is quite small too.
Be assured, everything Bronica is pro gear with pro performance, as is Mamiya, Rollei and most other marques you care to mention.
The variation in quality we see in the 35mm and digital slr market is nowhere near as apparent in the MF sector, there might be the odd duffer kicking around but generally MF glass is top notch across the range.
Never shot any zeiss glass but I can say that I can't see a difference between my Mam 6 50 and my Bronica 50 besides a slight variation in WA distortion, and I put that down to compromises made in the design of rangefinders...