I studied Engineering in university (Electrical was my primary discipline, but in the first year we also spent some time on Civil, Chemical and Materials Eng) before later moving onto Software Engineering as a career.

To me, the biggest difference between SWE and the other "real" Engineering disciplines is about respect for the laws of physics.

Engineers from the classical disciplines have a deep understanding of the immutability of physical laws, and build mental models that accurately represent this as best they can. SWEs, on the other hand, have a tendency to build mental models that are more conceptual or metaphysical, and try and force these onto real-world silicon.

(This is somewhat idealised, of course. There are hack engineers that don't understand first principles in the slightest, just as there are software engineers who have no high-level understanding of the code they just copy-pasted from Stack Overflow).