Sorry but there is no way the Donner Party could of made it from where they were camped to relative safety to the West - simply no way. I have made the trip they would of made on horse back and it took two full days to get to Blue Canyon. No wagons, no one on foot and in the Summer.
I’ve driven through there a couple of times in the summer—can’t imagine it with 20-30 feet of snow. But, to your point, the Donners were the only group that didn’t make it—everyone else that year made it in. The part I didn’t realize until I saw the documentary is that the people in California were aware that the Donners hadn’t made it and sent rescue parties—four I think—to rescue them. The Mexican War diverted men to attempt the rescues.