> If one is at that level already, I don't think there's anything better than AWS ECS out there.

100%. To answer the OP's question: my nightmare is having to use it at all. I work with small, very early-stage companies whose applications by and large are not complicated. Perhaps at some level of scale and/or complexity, k8s makes sense. For the vast majority of the cases I see, something like ECS does everything they need, while being significantly more simple to understand, develop for, and debug.