I'm dismissive of it because I feel that training time can be better utilized elsewhere. Your videos showcasing nonsensical bunkai only confirms that opinion. No one is going to come at you in a deep front stance, performing a reverse punch. People fight in narrow stances in order to remain mobile, which is why double leg takedowns are so effective.
I am very surprised that you made this kind of an assertion, especially considering that you claimed a nidan ranking from an authentic JKA dojo. At the Shodan level, just about any adult holding that ranking has a better understanding of how using deep stances are meant to strengthen the muscles of the lower body, and to teach the practitioner how to utilize the lower body as the main power source to drive the upper body's techniques.
When the body (and mechanics) are properly conditioned over time, when it comes time to throw a punch from a narrower stance, that punch will be significantly more powerful than one thrown by someone who hasn't practiced those mechanics, and conditioned the body.
It's basically the same reason why those who lift weights go through the full motions when lifting. Think of it this way...
Who is going to benefit from the bench press more? The person who starts with the weights at the chest level and lifts it to full extension of the arms, or the person who starts with his arms extended already, and only lifts the weights about 12 inches instead? Even though the latter may look more "practical" in the real world, it won't help the person nearly as much compared to the former when it comes to increasing overall strength.
Will the former allow a 150 pound beanpole to be stronger than a 250 pound individual built like a brick outhouse? Of course not, but neither would the latter. He would, though, certainly have better muscle development using the former, than the latter. It's all about developing his own self so that he comes closer to his potential, instead of comparing him to the next guy.
Personally, 30 minutes of hard, full contact sparring against a variety of opponents would be a better use of training time than 30 minutes doing pre-arranged patterns from the 1920s.
And how long could you continue to practice in such a way? You can't stay young forever. Joints become less flexible, bones become more brittle, and well-developed muscles deteriorate over time as we get older.
I would encourage you to look at your old notes from your days of Shotokan training. For that matter, you may want to have a chat with your old sensei about this subject.
Many of the JKA seniors have written articles about how the "old methods" of training continue to thrive in today's society, since they can be practiced for many a decade, and the practitioner will not see any dropoff in his technique when relying on good bodily mechanics and fundamental technique, instead of sheer brawn and athleticism.
If you get a chance, I'd also recommend some of the books written by Enoeda Sensei, who was quite well-known for his amazing punching power, even as he grew old. They can provide a very nice insight into the methods.