The problem with traditional arts is that they don't evolve, so seeking "deeper meaning" is kind of pointless if you're not introducing new methods.
I think they still evolve but not by adding. If this was true then boxing would have never evolved.
The issue with traditional martial arts and it's evolution is that there are many teachers of it that actually don't try to seek deeper meaning of it. There are many TMA teachers who can't use the techniques that they train nor do they have any interest in doing so. To be honest, there is nothing wrong with this unless you are trying to use the system for fighting. I believe a system for fighting can only evolve by fighting. If you want the system to remain a good fighting system then it cannot evolve in absence of fighting.
The truth about many TMAs is that they are evolving. They just aren't evolving into fighting systems, they are evolving into entertainment performance and acrobatic systems. The only reason's they are evolving into these systems is because the majority of the people aren't using them for fighting.
You can always introduced new applications of something that already exists.
For example, Jow Ga teaches a punching technique that I actually use as a grappling technique. No one taught me this application of the punching technique. I learned it on my own during fighting. So my discovery could very well be an evolution of this punching technique. Or I may have discovered that this grappling application was always there from the beginning and it's just that teachers weren't using the techniques in sparring. As a result they weren't ever going to discover this by not sparring with the techniques.
Fighting techniques cannot evolve without actually fighting / sparring. I can't just do forms all day and hope to evolve, improve, or understanding an existing technique. I actually have to use those techniques. The more I use those techniques, the better the chance will be for it's evolution.
The more people played the flute the more the flute was able to evolve.
The more peopled boxed, the more boxing evolved.
Most of the people you are referring to about TMA probably can't even use their techniques so how are those techniques going to evolve for fighting if you can't use them? You have to use what you train, if it doesn't work, then figure out what you were doing wrong with the technique. Gain a better understanding of the technique and try the new theory. Eventually you'll get it right, but not after a bunch of failures.
It's the same process as the invention of flight. Plane didn't fly this time, what did I do wrong? Rethink your understanding of the concept of flight. Try again. Got it wrong again? Rethink your understanding of flight. What are you getting right? what are you getting wrong? Try again. Eventually you'll gain the understanding your need to fly
My training takes a similar path. Some guy in the past was known to use these techniques for fighting. use the technique in sparring. The technique didn't work this time. What did I do wrong? Rethink my understanding of the concept of the technique. Try again. Got it wrong again? Rethink my understanding of the technique. What am I getting right? What am I getting wrong? Try again. Eventually I'll gain the understanding I'll need to use the technique.
Once I understand the technique, then I can start improving on the technique and evolving the technique. Similar to how the jab and footwork evolved for boxing.