And I don't agree with your statement. Blender is a great example for this. Although it is not constraint based it is a full feature package which is very fast. Compare this to 3dsMax which is exactly what you describe.
Fusion 360 on the other hand is not a scratch-built product, but uses the same kernel as Autodesk Inventor, ShapeManager - which is based on ACIS, of which version 1.0 was written in 1985. That gives you an idea of how friggin hard it is to write a decent CAD kernel - all the commercial ones are decades old.
The only real free software CAD kernel is OpenCASCADE.
Disclaimer: I am an amateur when it comes to 3D modelling, but I was able to figure out pretty much everything I needed to make things in Lightwave back in the 90's, but even after watching several tutorials I still struggle with Blender.
I know some folks that are a lot more experienced than I am, with 3D modeling, and they all say that Blender is very powerful, but the UX is incomprehensible. At least one of them is MENSA-level smart, so that says a lot.
I’m wondering if Blender is sort of like X11, where people have been declaring the end of the Microsoft/Apple hegemony for decades, or GIMP, where people have been declaring the end of the Adobe hegemony for years.
I will say that I am very impressed with the quality of the 3D work being done, these days. I see works like Worth Enough?[0] (which is actually over a decade old), and believe that 3D art is now every bit as valid as “classic” media. I suspect that the tools are a big reason for that. When oil was added to early media like tempera, the quality of art improved. I think that Blender is used for a lot of this work, so it can’t be that bad.
[0] https://www.deviantart.com/radoxist/art/Worth-enough-7324787...