

Most of the languages you’ve mentioned aren’t systems languages, so don’t make being a good language to write an OS in a high priority. More languages might be accepted in the future, but if they are, it’ll be ones that are a natural fit for the problems they’re solving.
Plenty of plumbing is done with moulded plastic pipes and fittings, and I’ve 3D printed garden hose fittings (things like GHT to BSP adapters, which aren’t easy to buy) with success, so it’s not like moulding is the only way to make plastic good enough.