I'm a middle aged +, amateur user/enthusiast. So, I'm really asking. Lastly, I wonder if the Linux kernel is like the Weasley house in Harry Potter i.e. kind of a monster with parts on top of parts , with the whole being more unruly and although functional is a bit of an unruly mess at this point that doesn't resemble anything like a good overall design like a good "new" house could be. Again, just asking. Most of this is well beyond my understanding.
More seriously, I believe the historical challenge with microkernels for Unix(-like) operating systems was the performance hit taken when transitioning from the user processes to the microkernel.