there is also rkt, and anyways, while docker containers are great, they are just an abstraction of cgroups and namespaces, yet you forget that cgroups are a relatively recent concept in Linux and docker containers didn't even have namespaces in its first, second of third iteration, yet you act like docker relies on the immutable principles of posix.
Anyways, docker is a good example of how current linux systems are not optimized for modular sandboxing and containerziation. Still, people are so uneducated even in tech on how important this idea of only working with bare bones (I started in C so allocated bytes as I needed them and always considered how not to use them first, is a far cry from npming an express server and seeing the endless train of dependencies that are invoked) that still they do not secure their containers, and the number of ubuntu18.04 std base images I see running a docker container that simply contains a python app or something equally trivial, live in production at some of the top tech companies, which you can google and download a rootkit for, with no linux hardening whatsoever, is the terrifying norm of centralized web application companies today. I really am not going to buy into this idea that docker contiainers baring full replicas of the operating systems they sit on top of are a justification for POSIX.
If you want increased modularity for security, sandboxing and running different application, look at QubesOS, which is already far along and has it's own baremetal hypervisor, which is much like how docker works in userspace but optimized all the way to bare metal hardware. Fuschia takes a similiar approach when looking at optimizing modularity in mobile computing hardware architecture.
" Also, several other mobile operating systems that did not quite make it or continue to struggle."
This is true, but this is coming from the same company who has experience designing both software and mobile hardware architecture. Just because something is not already popular and widely adopted isn't a reason not to do it. I'm always an anti monopoly person myself, especially in the world of technology.
You can read my other comments and see the justifications around the need for this. As someone coming from the hardware architecture design space for qualcomm snapdragons all the way to 14nm iphone architecture, there is a need to remodularize kernel for advanced execution and increased competition in this space. POSIX is not sustainable looking 10-20-40 years into the future of hardware computing, particularly in the next ten, and android game developers who make a living off of candy crush do not really seem to care about this impending doom, only that they will have to traverse yet another learning curve if the platform gains adoption or become competitive in the space, which sucks, but it's not as bad as you'd think.
Besides, forcing people to continue to traverse learning curves keep the market competitive and keeps people from becoming to religiously entrenched that google's current android API is an unattested god. Yeh, its hard to make money sure, it's competitive sure, but we so easily forget android was a first stab and open source response to the iphone. The first motorola android phone came out my sophomore year in college. Now people can't imagine how we would survive without their 6yr olds going to school without an iphone 7. We often assume we need things to be the way they already are, and are not accustomed to change, but I can tell you Fuschia is needed in the space, operating system competition is needed in the space, and in the next decade we will be evolving to think different about excessive use of memory, dependencies and latency and be looking for something like this, luckily it will be about a decade into development at that point, about what android is now, and people say it's unreasonable to consider anything else..