I think mechanical engineers mostly use 3-D CAD systems by now — SolidWorks, Autodesk Fusion 360, or something, not AutoCAD. EEs don't use AutoCAD; they use EDA systems ranging from schematic capture and PCB layout (like KiCAD) to HDL synthesis systems, and they use SPICE, and they write a lot of C++. AutoCAD is useless for any of those things. I don't know what bridge builders and airframe designers use nowadays, but given the importance of 3D in those realms and your batting average on the things I do know about, I'm guessing they don't use AutoCAD either. I'm interested to hear what the truth is, though.