By essential, it is what most engineering disciplines have in common: Good logical reasoning, and spatial thinking/skills, ability to build up complex systems

By essential, it is what most engineering disciplines have in common: Good logical reasoning, and spatial thinking/skills, ability to build up complex systems from smaller ones, and ability to understand/debug how complex systems work, and no 'magical thinking', but ability to analyze things logically. I am seeing here a bunch of answers that mention 'communication', 'write docs', etc... etc but those are essential skills for any employee in a large company, no matter what the discipline is. They are not core engineering skills per se (though they are necessary to perform in a large company). If you can't code, or don't understand concepts your communication skills will not help you that much. Maybe become a PM, or some kind of manager, but not an engineer. P.s I know communication is not core, as i have worked with many 'brilliant' engineers that they had poor communication skills due to be foreigners, or just personality quirks. While that will hamper their ability to get promoted to managers, or architects, they all were respected and did well as engineers.