Arch is great if you want to customize your system, but I wouldn’t say it really needs “maintaining” beyond just updating more frequently. (which you don’t even really need to do very often, you just have the option to get newer versions of software.)
I think you’re missing their point, they weren’t saying that Blender is cad, it’s just a good comparison, as a successful piece of software in the the same broad, general category (3D modeling)
We want what Blender is to mesh modeling, rendering, etc, but for parametric cad, manufacturing, etc. Basically Fusion 360 but open source, without any of Autodesk’s bs. Ideally it would even work together with Blender for rendering.