Agree that the 80% of injuries across the board can be prevented mentality comes from the same drawer as George Gregan's "caffeine improves your rugby game by 7%".
However, there is no doubt that sports injuries can be prevented much more than they are to date. It is equally magical to think that heart disease can be prevented and cancer can be prevented and road accidents can be prevented but that there is something special about sports injuries that means they are inevitable.
Obviously the analogy with other diseases can be continued. We certainly know HOW to prevent a lot of heart disease, but if the population sits on their collective fat butts for longer, all of the cholesterol lowering drugs in the world aren't going to cancel out the lifestyle-negative factors. In sports injuries, we could, for example, insist on depowering the scrum in rugby union, so that cervical fractures were eliminated via this mechanism. Will rugby union change the laws? Answer is perhaps eventually, when those in the sport become accountable for the rate of injuries, which currently isn't being recorded all that accurately. If for example it was compulsory for all players on the field to have $4 million insurance cover against quadriplegia or else the game couldn't go ahead, the scrum laws would change overnight (because the players wouldn't cop the high premiums).
The small decline in injury prevalence over the period of the AFL survey has shown that even at elite level some gains can be made. The trade off at elite level may be the standard of games, which needs to stay fast enough to maintain spectator interest. I wouldn't have a problem at junior levels of football if they made it illegal to have studs on the boots. Sure, every player would slip over 1 time in 6 when he tried to sidestep, but no one would ever do a non-contact ACL. The game would be a worse spectacle, but at junior levels, who would care? It sure would be nicer to have rules which didn't leave 15 year olds facing inevitable O/A of the knee after doing their ACLs.