I believe model and concept can be equivalent, not sure about the required formal terminology in English.

Complexity is probably most formally modeled in entroy in thermodynamics, although it behaves in the opposite direction that these ideas and oberservations suggest it should.

It still asks questions about the reason for this complexity and there is no scientific answer aside from "propably accidental complexity".

Science is curious so it probably shouldn't be dismissed by unmet formal requirements that aren't specified. "Layman" is unspecific, so what would your requirements be exactly?