If you want to build each individual piece without licensing from Siemens/Dassault, then yes this would compare to a moonshot.
Parasolid, the CAD kernel owned by Siemens, is more than 30 years old at this point. The same amount of effort has gone into many of the other building blocks as well. OPENCASCADE is a FOSS CAD kernel but doesn't work well for real CAD, and support is hard to come by for companies building on it.
Most startups tend to license these tools instead of building them, but that comes at a large cost that must be pushed down to customers, hence the $$$$ cost of CAD today.
They also have a massive global team of really brilliant people working on NX and the related components. I'm talking former NASA employees who worked on components for the space shuttle or Mars rovers work there. That's the kind of expertise you can't really buy or acquire as an OSS project.
Plus, they are not shy about acquisitions. It's how they maintain their dominance. Any company that builds a remotely useful product in that space will find themselves sitting in front of a Big Fucking Check that's going to be hard to turn down. Anyone who turns it down will probably find themselves sitting in front of several patent lawsuits all over the world.
Parasolid, the CAD kernel owned by Siemens, is more than 30 years old at this point. The same amount of effort has gone into many of the other building blocks as well. OPENCASCADE is a FOSS CAD kernel but doesn't work well for real CAD, and support is hard to come by for companies building on it.
Most startups tend to license these tools instead of building them, but that comes at a large cost that must be pushed down to customers, hence the $$$$ cost of CAD today.