I am constantly designing parts myself. I just wish that instead of having many unfinished, unpolished products we had something with the level of Solidworks / Onshape / whatever.

FreeCad is getting somewhere but it is still way behind. The last thing I care about is what language was it implemented with.

OpenSCAD is quite polished (for a programmatic mesh modeler).

There is a soft-fork which adds Python:

https://pythonscad.org/

which I've found quite useful: https://github.com/WillAdams/gcodepreview in particular, working up a facility to write out DXFs w/ arcs