[m55au]

I think it depends on what he is specifically criticizing.

I have not designed a motherboard, but plenty of smaller digital IC-based schematics and PCBs and in my experience the most problematic part has been either erroneous or lack of proper documentation or bugs in ICs which there are plenty of.

What I recommend you to do is to compare the schematics of, for example, Thinkpad T420 and Keithley 2001 both of which should be available with a search. What you will find is that the former is a collection of specialized chips (including one for battery charging) with mostly datasheet reference design based implementations + bunch of mosfets for enabling/disabling/routing signals, whereas the latter has almost none of that and plenty of analog "cleverness" and "raw" digital design, let alone the power input, which in my opinion was totally overdesigned. Or take any oscilloscope, where you need to design not only a computer but also an analog front-end + high frequency signal processing, not only routing. And I'm not even going into the actual RF board designs which you are probably well aware of is more physics than electronics.

Again I am not saying that it is easy for any guy on the street, but "relatively easy" to understand what is going on on the motherboard as opposed to the actual complex stuff. So if you see a common fault among many motherboards you can probably conclude that that specific area of the design was bad and criticize that. Whether the criticism is valid might be another question, but I would not automatically dismiss it.

Edit: I will put designing a motherboard on my todo list.