Has MPC ever addressed the pros and cons of the 1156/1366 platforms and discussed their strengths and weaknesses such as PCIe buss limitations?
Yes, when they first came out.
When was the last time MPC actually got right into the guts of power supplies and explained what to look for in a good one.
Power supply articles don't sell magazines.
Magazines are about news
.. not an information library. Power supply technology hasn't changed, so why would they produce an article explaining something that has been around for well over a decade?
When's the last time MPC reviewed a video card, CPU, or motherboard even close to the depth of some of our more "respected" sites.
Depth requires space. Also, when MPC does review a new GPU family, they do it with the kind of depth and accuracy that only Anandtech or Ars Technica can match.
Hell a lot of this stuff doesn't even have to be "hands-on test material". Just hit the important points of the standards and how they are commonly implemented amongst the various mfr's.
MPC has white papers that describe all of these things and far more 'in-depth' than any magazine since Boot.
Are they perfect? No. They have to sell their magazine to a broad spectrum of readers or they'll go under. As a result, they have to provide a broad coverage. All PC enthusiasts will, eventually, evolve past it .. this is part of the problem with enthusiast tech magazines .. at some point, your audience will outgrow their need for you.
Sometimes, we come back. If you've been away from the 'scene' for a while, you may need MPC to give you a refresher course on what is new and great in the industry. But they can't be everything to everyone.