And resource sharing these days for SaaS and PaaS either occurs on the hypervisor level or the application level — the (usually Linux) OS is seen as a liability and necessary dependency for the application rather than a secure environment.
Also, current isolation technologies on desktop tend to be a lot less secure than mobile. If you assume Fuchsia, Android, iOS to be the next generation of OSes, then the trend is definitely to "secure by default". Whitelisting permissions instead of everything being allowed out of the box. Even the current generation of Linux containers is more of a bunch of resource management hacks, compared to e.g. hypervisor sandboxing or to a lesser extent, BSD jails.
Also, current isolation technologies on desktop tend to be a lot less secure than mobile. If you assume Fuchsia, Android, iOS to be the next generation of OSes, then the trend is definitely to "secure by default". Whitelisting permissions instead of everything being allowed out of the box. Even the current generation of Linux containers is more of a bunch of resource management hacks, compared to e.g. hypervisor sandboxing or to a lesser extent, BSD jails.