Nah it's not you, FreeCAD is perfectly usable for something like the above referenced knob but even mid-size assemblies really have problems. I personally find the workflow to be bad and irritating beyond my ability to express in words and I can't imagine how frustrating it would be as a new user to work it out for yourself while at the same time getting used to thinking of objects as collections of operations. It's a great lightweight program for people who already know what they're doing and that value FOSS, though. 1.0 really fixed a ton of the issues, but it still has the "Blender UX" problem that seems to plague all big FOSS projects...