It would be an incredibly stupid thing to believe, however I never said that or even implied it, but since reading comprehension doesn't appear to be your strong suit, let me assist you by making a simple concept even simpler....
Head injuries 30 years ago (termed being "Punch drunk") = bad
Head injuries 20 years ago (termed a "concussion") = bad
Head injuries 10 years ago (the popular term was "PCS, Post Concussion Syndrome") = bad
Head injuries 5 years ago (CTE is the new terminology) = bad
See, the common idea here is that head injuries have been known to be significantly damaging for many, many years....yes, they have learned more and more throughout the years obviously, but the results haven't changed, head injuries are bad.
On to lesson #2, are you able to understand something without knowing every detail? Concussions have been studied for multiple decades, it's fairly common knowledge (at least i had thought so) that concussions (especially repeated concussions) could cause serious, permanent damage...yet since they don't understand all the causation (ie why some people aren't as affected by repeated head injuries as others), how to repair damage and/or how to mitigate the damage, they still study CTE and concussions.
Rocket Science 101, you're welcome.