It's great that the new system "just works" for you. But I'm damned sure it doesn't "just work" for quite a few people. Your post basically says, "I don't have a problem, so you shouldn't have a problem," which is pretty much like saying, "I had a three-course meal last night. I don't see why you should be hungry!"
My first linux box still had XFree86, but all the configuration I applied to it was stuff I copied from my books. (Didn't have internet access at home back then.)
The first time I really configured an Xserver was with X11.
I installed a bunch of public internet terminals for a library, back in 2006.
Somebody thought it might be a 'good' idea to give them big wide-screen flat screens.
I took me all most 3 weeks to get them working with something else then 1024x768.
Figuring out the correct modeline was real pain.
I'm totally not the guy who says default works for me screw the rest.
I've been in this situation many times, mainly because of really exotic hardware or configuration scenarios that simply no one else has tried yet.
All I'm saying is that stuff got a lot easier, in the past 5 years.
The screen that costed me 3 weeks of my live back then, works fine out of the box with a recent X11.
If there was only X11-automagic an no way to overwrite it with manual config settings I would agree.
But since it is still possible to do stuff manually as well, the new system is a great improvement in my opinion.
I saved me a lot of headaches so far.
Also to my mind X need two things:
1) A lot of old stuff like the serial x clients mentioned before shouldn't be a part of the standard X11.
You should not rip them out totally since some guy might depend on them.
I don't know much about the inner magic of X11, but maybe it's possible to have some kind of legacy modules for those corner cases.
2) The automatic, configless part and the documentation need to get better.
Not needing to configure stuff is great help to linux newbies, but there will be always scenarios where it won't work out of the box.
That's what the documentation is for.
Also a switch to turn the automagic off for the real powerusers might come handy some day.
PS: My favorite hate config file is still sendmail.conf