I don't understand your argument... there are quite a few operating systems receiving active development. For that matter, just with the Linux kernel there are

I don't understand your argument... there are quite a few operating systems receiving active development. For that matter, just with the Linux kernel there are dozens of operating system distributions, several based on BSD and more still when you consider ongoing support for Solaris forks and more bespoke OSes (redux, etc) and clones (ReactOS, Haiku, etc). If YOU want another OS, there's nobody stopping you from developing, forking or otherwise funding the creation or developing one.