The strict definition would be essential complexity is only the complexity that would be required to implement in an "ideal system" (eg no latency, memory concerns, etc). By that definition you cannot just abandon all incidental complexity (as our systems are no where near ideal). Instead, this way of thinking is helpful for keeping the essential complexity implementation isolated and free from the incidental complexity.
The disagreement is on what (sub)systems are even necessary/important. Heck, we usually have trouble agreeing on what goals we are achieving. Once we settle on what truly matters, separating the essential is not that hard.
