Yes, modern processors are getting too complex to handle. The first P4 design had a twenty-stage pipeline, where at least two of the stages where just delays to give the electrical signals time to travel across the chip. Later designs have only increased the complexity. The control logic to keep track of all the different units of the processor and its pipeline is also getting out of hand. Simplifying the processor core and adding more of them solves many design problems, and lets you get away with far less complex control circuitry, which saves on space and power consumption.

I seem to recall there are some interesting insights on this in this article: http://arstechnica.com/articles/paedia/cpu/cell-1.ars