From the historical point of view, this heavy decoupling is associated with microkernels which fell out of favor with the rise of the Linux kernel. I think in this day and age, modern programming languages could make building a microkernel that doesn't fall prey to the shortcomings of MINIX a possibility.
Microkernels are IPC-heavy, right? What I rather imagine is having modules at source level, not kernel level. So the thing still compiles down to a monolith/hybrid, but modules are abstracted away and reusable.
The IPC overhead is very much manageable, microkernels tend to be a lot more responsive than monoliths and with paging for message passing the overhead is reduced even further.
Microkernels are much easier to optimize for multi-core CPUs than monoliths. The ´kernel modules´ from a monolith run as user processes in a microkernel environment so they automatically benefit from more cores.
