the most open source un-corporate un-malicious-intent CAD programs out there, like FreeCAD, are VERY convenient but also in a way completely incapable of replicating the end-user-power of pen and paper
and while you might use FreeCAD and then manage to export to some other program successful, you now have to learn that other program
whereas, when you pick up a shitty Bic pen to do your drafting, constructing tangent circles is the same geometry Euclid was using 2500 years ago
software has this tendency to ensnare people with conveniences, even if we don't intend it to, even if we make it very user friendly and end user programmable and provide abundant learning resources
you're still learning _this_ program, or _this_ programming language