I took lessons way before instruction underwent its transformation and didn't get that much better and now with video and radar, my swing is by leaps and bounds better even though I'm older and more importantly, I understand a lot more, most lessons circa 2000, I was not quite certain the why of what the they told me what to do. Granted, I think there were good teachers as you go back further in time, but the were much harder to find.
I believe when you say 'rigid', it implies a false dichotomy that is not there. Maybe for poor instructors, but I think it does a great amount of disservice to apply that label to all instructors.
The only hard line that exist, and has existed is between good and poor instruction.
I grew up playing cricket, both high school and state and have been under @iacas's tutelage for 3 years.
What I have learned is that the highest level of instructors in golf (as in any other sport or walk of life) are extremely intelligent and very effective in using the right blend of tools, and use very workable distilled instructions to suit students who come in all flavors of life.
A 'non-technical' but poor instructor can confuse the dog do-do out of you too. That has never changed.
I have one but only use it occasionally to warm up. If someone had a real casting problem in their swing, the Orange Whip could help. But if you have a reasonably good swing sequence, it won't help correct anything. It is too flexible for swinging really fast, so as a speed training, it will be ineffective.