The communication would've happened anyway. Now it just happens through a common mechanism with strong isolation. That all the most resilient systems, especially in safety-critical space, are microkernels speaks for itself. For instance, MINIX 3 is already quite robust for a system that's had hardly any work at all on it. Windows and UNIX systems each took around a decade to approach that. Just the driver isolation by itself goes a long way.

Now, I'd prefer an architecture where we can use regular programming languages and function calls. A number of past and present hardware architectures are designed to protect things such as pointers or control flow. Those in production are not, but have MMU's & at least two rings. So, apps on them will both get breached due to inherently broken architecture and can be isolated through microkernel architecture with interface protections, too. So, it's really a kludgey solution to a problem caused by stupid hardware.

Still hasn't been a single monolithic system to match their reliability, security, and maintenance without clustering, though.