signing a waiver would do nothing.... Lawyers famously work around them. I am however surprised they don’t have signs warning you enter at your own risk.
That's is more or less what I am saying, signs and warnings that you are not going into a cutesy Disney world but into a real life world full of vicious animals that will kill you and eat you if they get the urge.
To expect people to enter a wilderness full of grizzlys without the means to defend themselves from them is no less than murder, and to not warn them that this could happen is gross negligence.
The last time I was in Yellowstone, I watched a bunch of Japanese tourists walk down towards a Grizzly that was lying behind a log with only it's head showing. I tried to warn them that the bear was dangerous but they wouldn't listen.
When they were within about 50 yards of the Grizzly the bear stood up, roared and flipped the log like it was a match stick, the log flew into the air and the Japanese flew back up the hill into their waiting vehicles. A lesson well learned with no deaths or injuries but it could have been so much worse.
On the same visit a Japanese tourist was killed while trying to put his arm around a bison so his wife could photograph him with the Buffalo. Didn't work out well, but I am sure the wife got many exciting photos of the event.