It’s pretty reasonable to argue that were these things written again, less than 100% of it would be in C[++]. It’d also pretty reasonable to argue that that percentage will be even smaller 5 years from now.
Sure, but that's a theoretical scenario, because this type of applications won't be written anymore. Anything that's relevant in those areas had been started in the early to mid 90's (even the 'newcomer' Blender had been released first in 1995).
...which unfounded assertion would that be? As far as I'm aware there are no contenders which would even attempt to throw tools like Maya, 3DSMax, Blender, ... from their throne. And all those tools hail from the 90's.
The only exception in recent time which gained some traction might be Figma for 2D design, but even though it runs in browsers the important parts are also written in C++.