There are three elements involved here, each of which are critical to the outcome:
The course subject and material - is it a relevant subject and is the course material well designed. Unfortunately, a course has to be designed for the masses rather than the individual, which means we are pitching to the middle 70%; the people at the margins are left more to their own devices. The only thing attending the courses do for them is to document that they have been exposed to the material. We have some regulars on this Forum who already have as good or better a handle on the material than some of the instructors - sorry, but if people hang out here long enough a lot of them are going to find the USPAP update course to be nothing more than the same old thing.
The presentation by the instructor - even a good instructor can have a bad day, one where they are unable to find their rythym or properly sync with the group of people they're teaching. Not only is a course no better than the instructor, a course is no better than the instructor is on that day.
The attitude and aptitude of the students - it doesn't matter how good the material and/or the instructor is if the student cannot or will not make a fair attempt at getting something out of it. Some students come in with a hostile attitude toward the subject and the requirement that they have to spend their day in that class, and they decline to pay attention or to make an effort; so it comes as no surprise when they finish they have the 'proof' necessary to justify that attitude. Not surprisingly, these people are usually the ones who have the least realistic interpretation of the role of USPAP in their appraisal practice. They often tend to think they know a lot more than they do, and they take the "everyone does it" rationale for disparaging the material.
Then too, there are a few appraisers out there who lack the aptitude to understand the material, often as a result of lack of competency with the English language. Hopefully they do better with written materials than they do orally. I believe that there are a few people who basically lack the intelligence to substantially understand the material, but fortunately those folks seem to be very few and far between.