As others have also pointed out just dropping people into a new environment is completely abnormal and in actual history the situations one would have expected to see this was during large volcano eruptions dropping the global temperature and when that did happen we had mass starvation and death so its not like people living off the land handled such situations all that much better. It also wasn't just humans that died in such situations many animal and even plant species suffered large dieoffs.
Also genetic studies of remains of Native Americans show that entire tribes died out repeatedly in 200-300 year time frames and new ones moved in.
We are learning that weather pattens are not just a seasonal and annual thing, that they come in cycles across hundreds or even thousands of years that would render areas unsuitable/suitable for human habitation.
California for example has dry and wet stages and its wet cycle is ending.
California if it suffers a full dry cycle will have to use salt water distillation plants for drinking water and agriculture and industrial water use will have to stop almost completely.
USA does not produce enough power in total even if it was all used to distil water at 100% efficiency required for Cali agriculture/industrial use.
Even modern technologically advanced civilization is not immune to weather cycles and its even possible the drying of the western cost of the USA could seriously threaten the USA as an entity if up to 1/3 of its people have to relocate due to water loss.
So seeing how people are at surviving when dropped into a random environment just goes to show how fragile we really are, something people living in cities and getting water magically from taps and food from magical shops where it appears on shelfs often seem to give no thought to how fragile the entire system is.
It kind of bothers me that none of the teams have thrived in their new environment. People have lived for tens or hundreds of thousands of years in some of these environments and the best trained modern men are spent after 3 weeks... Seriously?