I think a lot of what we're seeing is not indicative of "normal" football play. We see people who played professionally, in many cases well into their 30s paraded out as examples of what football can do to you, but do you know anyone who had a physically demanding profession that they did for over ten years and doesn't exhibit signs of wear and tear? I don't, it comes with the territory. Where my dad worked there were guys that died on the job, guys with missing fingers, guys who got cancer, heck my dad got an asbestos settlement. My dad died of cancer in his 60s, how do I know it wasn't work related? They are not going to do a multi-million dollar study on that though. Does that mean you shouldn't try to make a safe work environment and accept inevitable consequences? Of course you should try to make things safer, but people simply have to accept that some professions are going to come with certain dangers. Racing, boxing, MMA, but not just sports. Firemen, miners, soldiers, etc... one can easily compile a list of professions that are extremely likely to produce long-term consequences.
If one really wants to avoid the pitfalls of those things, then one shouldn't wait until your body is broken down to get out of them. A soldier shouldn't wait until he's forced to resign, a boxer shouldn't wait until he can't physically stand in the ring anymore, and a football player shouldn't wait until he can't play the game anymore. This is more about knowing your limitations than anything else. Everyone always knew football over a matter of decades could cause harm, this was never up for debate. The key is to know when to give it up. We simply can't criticize players for retiring "early", because what they are really doing is retiring at a point in time in which their injuries are minimal.
Another thing we are missing here is that most people who play football are not dealing with major issues for the rest of their life. Look at Nick Saban, how many people do you know his age that have his mental sharpness and his physical mobility? He's a product of football to and this is what people forget. This is a game that can be good for the individual playing it, this is a game that has health benefits as well. I'd argue that if the choice is between your kid sitting on a couch eating a bag of chips or playing football, he's probably going to lead a healthier life if he chooses the latter. And that's a key point. Don't confuse a few years of amateur football with playing at the professional level for over a decade, it's simply not the same.
Then, we have the scientific side of things. The data is not really conclusive yet. It appears that playing football can lead to certain changes in the brain but the exact implications of this are unknown. The obvious thing here is to try and protect the head from harm. The one thing though is treatment and that's part of what we are not really looking at here. In the past, these issues were compounded. Someone would get a concussion, then continue playing while their brain was not healed. Healing, proper care, etc... are all frontiers that science needs to focus on in this case. It's not just about avoiding injuries (which can be incurred doing almost anything), it's about how to treat and heal these. I think that's one of the biggest issues in this entire situation, they acted as though there was no damage at all and anyone who has injured something and then tried to go on as though it's not usually found they only made it worse.
Finally, there's the fan aspect. I'm sorry, but unless they make the game unwatchable, I don't see it as dying out. You know football was originally almost banned right? That boxing was banned? MMA was severely limited in the beginning, etc... There's an appetite for these sort of sports both from the fan perspective and the player perspective. If you want to hit somebody, it's darn sure better to do it in a ring, or a cell, or on a football field than anywhere else for example.