In the famous Torvalds - Tanenbaum discussion Torvalds got it terribly wrong, but Linux was good enough to get off the ground anyway so in the longer term might made right. But a microkernel based Linux would have been a serious game changer rather than a re-run. After all we already had plenty of free Unixes back then, and the descendants of those are all still more or less alive today.

The major sticking point in that whole discussion is that Tanenbaum may have been right in principle but Minix was not a very good illustration of what a micro kernel could look like. QnX on the other hand was awesome and to this day powers a very large chunk of the embedded sphere.