I loved the idea of FreeCAD but having no experience in CAD software at all I always struggled with fundamental basics that were not covered in the tutorials I watched. The huge amount of work benches (some of them 3rd party) did not help since most forum posts or tutorials were based on different or outdated versions.
Having a go with build123d now, trying to model stuff using python. At least the number of available API functions is manageable and everything else is just programming (which I already know).
Yeah I think most complex and long-term OSS projects have “employed” contributors paid by donations or sponsorships (e.g. Linux, Blender, LibreOffice, …)