I certainly haven't said that Tom. I believe the agency impacts the student more than the individual instructor, as it chooses who is to become certified as an instructor (establishing instructor standards), they can restrict the instructor as to what s/he can and cannot teach to an OW student (very agency dependent), restrict how and in what order the student is taught and establish the standards upon which a diver is to be certified.
There are HUGE differences in agencies and the degree of restriction they place on the instructor and what the instructor can require for certification over and above the minimum. In fact in some agencies the instructor must teach/examine to the (minimum) standard.
Granted. However a great padi instructor can teach a better and more comprehensive course than a crummy naui, ssi, sdi, etc instructor(Im assuming you are talking padi when refering to not being able to go above and beyond). The agency has very little to do with the quality of instruction after the ITC is complete.
Yes there are instructors(including myself) that teach challenging and comprehensive courses, but to say that all Naui instructors are that way just because I am is un realistic.