Warren Spector is retiring from game development
IndustryComments
The full article mentions that his health issues specifically made the current culture of crunch unsustainable. The shift isn't just in the design philosophy, but in the physical toll required to ship a modern AAA title.
I would argue that systemic agency isn't necessarily harder to implement technically. The real bottleneck is the exponential increase in the QA matrix; testing for emergent bugs in a modern open world is an order of magnitude more complex than it was in the 90s.
The 'shift in the business' is usually just code for the live service pivot. You can't build a truly unpredictable systemic world when you have to maintain a strict monetization loop and a weekly patch cadence.
It's basically the Theme Park effect. We've traded actual agency for a polished, cinematic checklist because predictable beats are safer for shareholders than emergent chaos.