not totally disagreeing with you. You bring up some interesting points for sure.
I think XC has pushed design quite a bit. The development of quality full-suspension xc bikes, lightweight components like hollowtech cranks or the use of air for shocks... the liberal use of carbon fiber and the advent (with the 2003 XTR) super light disc brakes.
I really believe the XC quest for lightweight but tough equipement has pushed design forward and made some real improvements for everyone to build on. Just like DH bikes do.
Freeride bikes owe alot to XC development.
As for courses... well, I enjoy what they have. Have you seen Houfaluize (sp?)? That is some wicked stuff. Don't forget that XC is about speed, technical and athleticism (please no tit vs. tat). The fact many XC riders are making the jump to road give alot of cred to XC and mountain biking in general. I think that crossover ability says alot about the great type of athelete XC develops.
Also, XC is a sport and freeriding is an activity. Not putting freeriding down by saying that but that's the way it is. Maybe one day freeriding will become a sport (makes the name "freeriding" an oxymoron then!)...maybe XC+ or something!