Iirc microkernels have been the future since before Linux existed. There was a bit of a flame war between Linus and the guy who wrote the MINIX kernel about how being monolithic would be the death of Linux.
GNU Hurd also wanted to show the world how good microkernels could be, but sadly never got off the ground.
I’m not saying microkernels are bad, but I do wonder if there’s some reason we don’t see them out in the wild much.