HarmonyOS is a modern (post-Liedtke) microkernel, multi-server OS.
Meanwhile, the rest of the world is stuck with the likes of Linux (monolithic), Windows NT (ugly hybrid) and MacOS (pre-liedtke Mach, hybrid, ugly).
Good technology exists (e.g. seL4, genode, RISC-V) but we seem to be stuck investing into bad tech.
The game changer part is of course in terms of the broader tech war. What we have here might be a consumer operating system that is technologically better than what is on offer from Apple, Google, and Microsoft. Built by a vilified Chinese company.
There are reasons nobody uses true microkernels. IPCs are slow and the gains are limited compared to the strategies all broadly used kernels already use. They are no monolithic kernel anymore. Everyone has slowly but surely been shifting more and more things to user space in isolated processes including Linux and Windows.
Hongmeng might be an interesting kernel. It might also not be. Sadly its proprietary and there are very little benchmarks not published by Huawei. Personally I won’t hold my breath for this one.
The problem you are describing is a characteristic of 1st generation microkernels, and was solved by Jochen Liedtke in the mid 90s, introducing 2nd generation microkernels.
seL4 is a 3rd generation microkernel.
>I don’t know what "modern" microkernel means.
To get up to date, a good resource is Gernot Heiser's blog[0], read from oldest to newest.
Even SeL4 fast IPC which is not actually a full IPC but works well in the barebone context of SeL4 remains in fact slower than good old syscalls.
The fundamental question remains the same “Is this worse the costs (in terms of both efficiency and design complexity)?”
To me, the answer is muddy here. Sometimes yes, sometimes probably not. I think it’s why hybrid approaches are now generalised but no one is really shipping a microkernel outside of industrial applications.
Unless it does, it is unlikely there'll ever be a year of the hurd desktop.