I like the idea how it will be such a problem with Lockhart while you will be able to play the same games on 536 different PC configurations and no dev will tell you how it's so much work to develop for all these configs.
No they don't. They have a baseline of what they are aiming for. They just give you options to turn certain effects off and lower the resolution so you can attempt to get it to run on lower spec machines. They aren't testing all of these out. If your PC doesn't run it well, they aren't going in to make specific changes to get it to work, you just need to update your HW. On the Lockhart, they will have to do extensive testing on it to getting it running 1440p/30fps/60fps on a system that has a much weaker GPU and significantly less RAM. Sure, you probably will get games that drop into the 20fps range and have variable resolutions, but MS isn't going to be happy if this consistently happens, or the games are dropping into the teens on fps and 720p for the resolution. That will turn gamers off from getting this "next-gen" system.
This is why devs, not just gamers, are complaining about this. They feel it's going to hold back their games and/or cause them to put more resources into getting those games running on Lockhart.