The goal of the KiCad 3d model library is to provide a free open library of 3d models. The use of open source design tools is preferred for this very reason.
Freecad is chosen as the preferred tool to be used. Especially in combination with the kicad-stepup extension.
Good alternatives are open scripting options like OpenSCAD or CadQuery. For the latter consider contributing to https://gitlab.com/kicad/libraries/kicad-packages3D-generator
Files created in closed source tools are permitted. If a certain model is available designed in both an open and closed tool then the one from the open tool is preferred and will replace the other one.