Clearly You haven't watched in about 5-6 Seasons. The creators got sick of having to make up new ways for Kenny to die each time, it was beginning to become a drag, so they pretty much dropped it.
I love the Show, Its a good show and I don't really think they went TOO far. The joke wasn't aimed at Cancer Patients, it was aimed at movies that show that a big victory in a sport always leads to the miraculous curing of a terminally ill patient. But still, I can't say it was my favourite episode (it just didn't seem to have a point, and little to no involvment from other main characters)
Still, South Park is a very underrated over show here (at least I think so). Its always fmily Guy this, Family Guy That... But South Park episodes follow a storyline, and the characters show angles and emotion co-ersive to the story, not just cut out after cut out, like Family Guy (Although Thats a good show too, but I still favor South Park)