Earlier quoted context omitted.
So, you're asserting that the color choice of the bubbles ten years ago was unintentional? That whatever developer coded it had no instruction, Jony Ive & Steve Jobs were silent, and they used a random number generator to pick the hex code? And additionally, you're asserting that its impossible to change or improve? That its just such an intractable problem which we inherited, and changing it would be such a herculea…
I'm asserting that a decision was made that SMS messages were green. Then a decision was made that iMessage messages would be blue. I'm asserting this was not done with animosity. It was a decision by Apple's UX team to make it easy to visually identify the difference between the message mechanics and capabilities of the end-user. It is remarkably simple, effective and easily understood. If Apple chose to make it so…
Also, I'm not asserting that Green is bad. The issue is the shade of Green, and the a11y issues it creates. I don't know how you jumped on "entirely different colors" or "the same color"; Android's criticism in the original article is very clear, its an a11y contrast issue with the light green background and white text. That's it. Nothing else.
This issue is, seriously, a lot simpler than you're exploding it to be. Make it 10 shades darker; done. They even have an option in their accessibility settings to make it so. This is a simple change, any a11y expert (including, maybe, the MANY apple themselves employs) would say the way it stands today is bad, but their inaction conveys intention.