I remember Linus Torvalds mentioning, that while the 386 was a complex CPU, he was able to understand it on a sufficient level. But this time seems to be gone.
DRAM is even "easier" because it's just a repeating grid pattern. Tuning the cell design is important for performance, as are the read sense amplifiers at the end of each row, but once the tuning is satisfactory you just get the software to make N copies.
Possibly the most overlooked part of the process is the bits that aren't either taught or written down but passed on in the oral culture of the engineers. Analog IC design is a lot more like this.
I don't think that there is a single person to understand a modern, complex CPU and its production in full details. Take, for example, a datasheet of modern CPU/SoC -- it's thousands of pages of dense, technical information, and that's already a (comparatively high level) abstraction. As one professor told us in university: technology systems are getting more and more complex very fast, and soon (if not already) the biggest problem will be that noone fully understands how things/infrastructure, our society relies on, works. UML[1] and similar solutions alleviates this problem to some extend.