Have new divers like myself missed important and useful information that was taught pre-1983? What has changed?
It is not clear that what has transpired is a 'dumbing down' of training, as much as a minimalization of the requirements for initial certification. If you go even farther back in history, there was a period when you didn't need to be certified at all to dive. Diving and dive training was in its infancy and a number of people learned simply by doing. There is a very well known underwater photographer - his pictures appear in many publications and he has authored numerous books on marine life identification, among other things - who only became certified a few years ago after diving (uncertified) for more decades than many divers, and some instructors, on SB have been alive.
Or, students learned through what amounted to an apprenticeship, where individual instructor discretion regarding what was essential, and individual instructor judgement and assessment of the student's fitness for certification, was the norm.
The formalization of dive training evolved from several sources, including a significant military process influence as well as a less extensive but equally important academic organization influence. These converging factors led to the development of standards that were perceived to be 'high' or 'rigorous', but not necessarily 'market friendly'. As the diving community expanded, and the market for equipment and training grew, it became a more market-driven process, as noted.
A number of things have changed. As some have said, not all is good, not all is bad. Perhaps, the biggest change is that the threshold of knowledge and skill required for initial OW certification has been moved. If you think of a continuum of knowledge and skill as a straight line, running from the left which is 'minimal', to the right which is 'extensive', the threshold for initial certification has moved to the left. The continuum itself has probably broadened, so there is more room to enhance your overall knowledge. But, the initial requirements are fewer in number, and less stringent. As an example, at the OW level:
1. The physical requirements have been modified and are no longer as demanding.
2. The academic content has been reduced, and there is far less emphasis on diving theory. Some of what was previously included is now taught at the Advanced Open Water, Rescue Diver, or even Divemaster level, for example.
3. The process of 'diving' has been compartmentalized into certain basic skills, that are 'mastered' on an individual skill level, with less emphasis is placed on the formal integration of the skills. You see comments on SB about skills being performed 'kneeling on the bottom' of a pool, or on an underwater platform, vs being performed while neutrally bouyant in the water column (with the former approach viewed with disdain, even scorn).
Have you 'missed' information? Probably. Much (but not all) of the skill training and information is still there, it is just presented at a different (later) point in the diving instruction process.
Three suggestions to gain a better understanding of this evolution.
1. There are a number of threads on SB addressing this topic. A particularly useful, recent (and still active) thread involves discussion of what standards need to be changed. A search on 'standards' might help you locate this and other informative threads.
2. There are some on the forum that point to the content of the 100 hr Scientific Diving training programs, offered through a number of universities, as the gold standard for dive training. There are a number of university websites that list the contents of these types of program, such as the one at University of South Florida, and I suggest you take a look at
www.research.usf.edu/diving/diving.htm as one example.
3. To the extent possible, take a look at the OW requirements / standards of different agencies, including PADI, and you will see subtle differences, about what is taught, when it is taught, or how it is taught. I don't think that, at the OW level, the standards are materially different in terms of the ultimate safety of divers certified under those standards. At least, there are no objective data supporting that situation, notwithstanding many anecdotal assertions that such differences exist.