> I'd say that Linux's popularity tend to translate to technical superiority
Linux isn't exactly technically superior to other OS kernels, and it's definitely lacking in innovation.
You cite Docker as an example, but that's a shining example of Linux taking major innovations from other OSes and copying it badly. BSDs had jails and Solaris had zones long before Linux got containers, and whereas those were considered security features on other OSes, Docker containers are not seen as improving the security of systems.
Other features like this exist too. Linux has refused to allow better IPC mechanisms such as what Android to be upstreamed, and the Linux replacement for select/poll is generally considered to be the worst of the bunch.
Another consideration is that both smartphones and supercomputers tend to use lots of modifications to Linux not present in desktop kernels. Android, as mentioned above, uses a different IPC mechanism, while supercomputer applications rely a lot on libraries that bypass kernels because scaling to highly parallel 100,000-core systems requires breaking POSIX a fair amount (particularly the filesystem semantics).