I get that they are ugly, but we are told that they are safer. If the NFL with it's billions of dollars can't create a safer helmet I would be stunned. That said, if I were the NFL I would tell players that it is not mandatory but if you refuse to use the safer helmet, you are waiving any future rights to sue or seek treatment.
As you pointed out, it was a subsequent concussion for Doubs so his brain already had a start on being scrambled. Had he been wearing it from the beginning, he may not have ever gotten a concussion. The CBS article below says that the correlated conclusion is that the helmets reduce the overall frequency of concussions by 50%.
The answer is complicated, perhaps unnecessarily so.
www.cbssports.com
As for memory foam, my only concern is the heat. Memory foam retains heat and could cause more players to have heat exhaustion/strokes. Maybe there could be an intermediary layer to prevent that - IDK. Anecdotally, Mrs. El Guapo and I finally jettisoned our king sized bed and put two XL Twin mattresses next to one another, still using our king sheets. She is a side sleeper so has the softest, memory foam mattress in the store. I went the other direction and got the second-firmest mattress in the store. Most importantly it has helped my back tremendously. I don't wake up with a bad back anymore - just from being dumb lifting things! I also noticed that when I go to bed at night, my mattress isn't as cold in winter. Memory foam holds cold. I also don't get as hot sleeping because the memory foam traps your body heat. So my back is better and the bed doesn't have the temperature extremes due to the lack of memory foam.
One more memory foam point. At our cabin, we have several normal mattresses and then one that is complete memory foam (came compressed in a tiny box). When we go on winter trips, that memory foam mattress is like an ice cube until the fire gets the cabin warmed up. We have to take off the blankets to let the heat get in there. So if a team like the Bills or Packers were playing in another 5 degree game, those memory foam helmets could actually be worse...like Lombardi's dismay at Lambeau Field prior to the Ice Bowl.