IMO - it's got less to do with class time experience on the part of the instructor and more to do with exclusion of content, available content that wasn't used. And students who essentially throw out what they've learned.
I'd liken it to a cookie cutter. If you have a square mold every cookie produced from that mold is square. When a grandparent passes the cutter down through the generations to their progeny guess what cookies the grandchild will produce? Uh, you think round, no think again.
How does that illustration relate to scuba? If you don't teach all the material, if you don't tell students to stay off the reef (and show them how), to avoid dragging gear and to be streamlined (and show them how), to respect the environment, the aquatic life, and to stay neutrally buoyant throughout the entire dive - then how will the students do these things properly. If an instructor doesn't learn from their bad student product and review the course to include next time the things left out of the agency's program, if you don't make any changes that will result in better divers then what can you expect. What kind of students do you think that type of instructor will produce after they become "experienced", after their 1000th cookie cutter class? Uh, you think good divers no think again - bad divers.
If an instructor continues to leave out key points from the course, doesn't stress critical material, leaves out any of the building blocks, or continually repeats inaccurate material, continues to set a bad example, passes bad student divers, and ignores student problems again and again - anyone with half a brain will tell you a thousand classes won't make you any better.
PADI has made it possible for an instructor teaching their very first class without any assistance to produce good divers. I believe it because I've seen it, tried it, lived it ... and it works. The PADI OW program can produce quality safe divers. The fundamental issue as to why we have bad PADI OW divers - is not the material, it is an instructor who isn't applying the material, even if that is on their first class or their thousandth one.
I disagree with many here that the PADI OW program in particular has left anything essential out, there is enough on streamlining, buoyancy, weighting, aquatic respect, and flexibility for local diving environments to produce a quality BEGINNING diver for any recreational setting. There has to be some responsibility if the components were all there and the student doesn't keep diving the way they were taught. Those who drive a car did whatever it took to look good long enough to get a driver's license. So why then are our roads filled with dangerous, illegal, driving? So what, for 4 check-out dives a student looks great, follows everything they were taught to do. Then on the first dive without their instructor - they throw everything out the door. When it comes to driving we have cops. But it isn't practical to police dives. So maybe empower professionals to give out diving tickets <LOL>. Education is the key to increasing awareness. But there is more than one way to educate a diver. The next time you see bad diving embarrass the crap out of someone. Who knows they'll either be so offended they will quit or clean up their act. Every diver out there can make a difference in this regard. Make some waves spread the word.
Are there things the OW program doesn't cover - OH YES many, many things. And I can tell you that PADI doesn't have enough speciality programs, not even close, to cover all there is to know about diving. I've seen that for myself in technical circles and commercial circles. But as far as BEGINNING OW recreational divers are concerned - "it's in there". AND If all the resources which are available in the program are used by the instructor and if everything is practically applied - the program will produce a quality BEGINNING diver. Will these students need more education - don't we all? Will the learning ever stop? No. Every diver needs to "keep diving" and "keep learning".