I think a lot of the common idioms passed around about microkernels stem from the old Torvalds v. Tannenbaum argument [1]. It wasn't that Torvalds was right and Tannebaum was wrong. It was simply that Tannenbaum had reliability and theoretical correctness in mind, while Torvalds was concerned with performance. The less context switching you do, the more performant your computer will be. We can take this to the extreme and look at OSes like TempleOS [2] where EVERYTHING runs in kernel mode. Most people prefer a bit more reliability, and so modern desktop kernels are generally hybrid kernels (with the notable exception of Linux which is, of course monolithic). I don't think there's any real technical reason a microkernel couldn't work on today's hardware which is many orders of magnitude faster than what we had in 1992, but a hybrid kernel is always going to be faster.
[1] https://en.wikipedia.org/wiki/Tanenbaum%E2%80%93Torvalds_deb...
[2] http://www.templeos.org/