I don’t think it’s because the players don’t care. It’s more of a combination of not being able to practice much in pads anymore and the art of tackling being much more difficult with all the rules changes over the years. The way most of us who played football as a kid were taught to tackle would get you flagged for a personal foul today.
In the end, I think the way football is played today is so very different than it was 20 years ago, the “fundamentals” are not as clear as they used to be. Tackling is not worked on enough today. Even though the rules have changed in how you can tackle, the teams who tackle well usually win games.