Moving fast is useful. Moving fast with structure is what makes it sustainable.
You need to have structure when you are moving fast, else it becomes chaos.
Coding agents have made coding faster, but they did not give teams the structure to move fast.
A software factory gives you that structure. It gives you a way to work with agents and review their work early in the cycle - PRD, HLD, design - before they go too far and create a mess downstream.
You can have accountable owners for each agent and each stage. They can review what agents are doing, nudge them when needed, and stay in control at every stage.
One can argue that coding is cheap now, so we can always refactor the code later. But refactoring is not just about rewriting code. Once something has moved downstream, you may have migrations, dependencies, and customers already using it.
Code can drift and can take entire different shape in few weeks if not taken care of. Its ok for vibe coded apps but if you are talking but serious scalable production code than investing 5–10% extra time early can save you days of refactoring and customer migration effort later, I think that is worth it.