Prepping will probably keep you alive and well enough to handle just about any problem for a long enough time for society to generally recover from most things that could happen to it.
However, if we are so up the creek that there is no recovery for years on end, there isn’t enough prepping anybody, but the most elite, could do and thrive.
Your statement isn't true. It takes intelligence and “some” money, but not an exorbitant amount, to prepare to live years without outside utilities/services.
One prepares to live as their grandparents in the late 1800s and early 1900s did. We could substitute solar power charging rechargeable batteries to help replace oil lamps and candles to produce light and run battery fans. It just takes planning and not a large amount of money to do it. Any water can be purified using a Berkey water purifier.
I wouldn't live underground with people I didn't know and their fuel for power will run out when thinking of years unless they are using solar power. That underground shelter depends on someone else to make it work. I depend on myself, not someone else to provide what I need to live.
My paternal grandfather was born not long after the Civil War. His first wife died in childbirth and it took him years to remarry, to my grandmother. Mourning I suppose.
From him, I know that there certainly is a way to live off the land. None of us would exist if that weren't the case. Wells were dug by hand. Cooking was done over a wood stove. You hunted, grew or foraged what you ate. You built your shelter out of materials that came from the land upon which it was built, log cabins with wood shingle roofs in the frontier east or perhaps stacked fieldstone, baked clay adobe in the west, sod shelters in the midwest, brick or quarried stone in more established settled areas. They made the brick onsite. Staples were all that were purchased and other than salt, you could get on without them. Oil for lamps, sugar, etc.
*******************************************************
That's a bit hysterical. Millions of people have lived without modern conveniences for hundreds of years. The people who settled this country were strong and without a doubt some of us will prevail - and it's not necessarily just gonna be a bunch of elite wussies either.