For private use strictly FreeCAD, at the job Inventor Professional. While FreeCAD is ‘not there yet’ in many regards, it’s a great piece of software -if- you accept the flat learning curve and invest time. But I understand what you’re saying. If you already have a solid understanding of CAD-basics, you rapidly understand what the programmers want to achieve and get there relatively fast. If you expect tabet-esque convenience (which I think from a professional standpoint should not be the goal for a parametric modeler) I get that people get frustrated.
Having tested OnShape years ago, where it already appeared very feature rich and smooth, I have no doupt one can for sure realize complex multi-part assemblies with it. For me the interesting part, in a professional environment, would be the software’s capabilities of its drawing module. Full digital workflows seem to gain track, but for me detailed technical drawings are still the bread and butter application of a CAD.