If you think about it, there is a difference between going into the wilderness for an indefinite amount of time, and going in for a specific period.

If you have plenty of time and no constraints as Nessmuk typically did, it doesn't matter if you have to hunker down for a day or two in order to make gear or fix broken gear (like snowshoes, just for an example). It doensn't matter if it gets dark and you have to stop for the night. And it doesn't matter if a big storm suddenly occurs because you just hunker down for a couple of days and ride it out in a sheltered spot. So in this case you don't have to carry a headlamp, a big hank of paracord, extra clothing etc and etc to deal with contingencies. Even if you become "lost" it might not be a big deal - you have plenty of time to get yourself unlost. With plenty of time available you can trade time for gear to some extent.

However if someone expects you back by a certain time or they will contact search and rescue, you need to take steps to help insure you can walk those miles even if darkness falls, there is a mishap, some essential part of your gear fails, no matter what the weather, etc. This kind of wilderness trip requires backup gear that adds weight you must carry.