Hm. I'm not sure I follow and I use Fusion regularly and FreeCAD a little. Does the property editor/spreadsheet in FreeCAD not count? You change a value, the dependencies get recomputed. Works about the same as in Fusion and certainly satisfies "parametric" for me.

(I use Fusion too, and think it's overall easier to use and more polished, it just seems strange that the lack of parametricity is what irks you.)