It is a complex issue. But the simple fact is the human head is not designed to get hit, our brains are basically floating in fluid attached to a spring. They also suspect that it isn't just major concussions either, but repeated lesser contact. The average lineman gets hit in the head probably 1200-1500 times during a season between games and practices. Even if they are not concussed imagine the force two 300 pound bodies create firing off the snap.
They are outlawing heading the ball in youth soccer because of it. It is affecting youth football too, and when you factor in the cost to outfit a youth football team compared to soccer or basketball it can't help but hurt participation.
The NFL is on a slippery slope for many reasons, but player safety is a joke. Zeke get 6 games for being accused of DV while Burfect targets a defenseless player and gets a game. Alonzo deliberately knocks out Flacco and doesn't even get suspended. Having teams play late games on the road or night games on Sunday and then have to play on Thursday is beyond unsafe. 4 or 5 preseason games.
Yes players get paid, but the average career is short and most players make under a million a year so it isn't like pro baseball and basketball. The majority of NFL players will never be a millionaire much less a multi-millionaire. For every Tony Romo retiring with 100 million in the bank and millions more coming in from TV, there are hundreds of players with little if anything in the bank that will be working at Home Depot once the league is done with them.