The real issue is that even a WARTIME boot camp can't compensate for 18 years of inadequate nutrition, weak bones, and being severely overweight. You can force diet people down, but humans raised on junk food with little exercise tend to have skeletal problems that can't be reversed and certainly not quickly.
That will put unfair pressure on the much smaller segment of the young population who managed to stay healthy: the athletes, the upper-middle class, homeschooled homesteaders, some old military families, and the like. Wealthy people will not want to send their precious darlings into a meat grinder.
It isn't about snowflakes; it is about physical reality. A friend in the military told me that these days, they are losing even highly motivated young people who look healthy but have bones so compromised that they break under the strain of a 25-mile hike or heavy backpack.
I have no idea how a modern military will deal with this. China is already cracking down and paying attention to what its children eat and how they exercise. It is coordinating some of its educational programs to ensure more physical activity and healthy (non-ultraprocessed food) in some urban areas. They are also trying to restrict the time severely spent gaming on computers (good luck with that, but they are trying). They started this about three or so years ago, but it will take the US at least 10 to 18 years to grow a new and stronger generation IF they start now. I can't see that happening, especially where "cannon fodder" drafted troops tend to come from.
This isn't the 1960s when most kids still rode bikes and even poor kids at what Momma (or grandma) put on the table, except for treats. Kids with natural whole milk in school and poor children whose school lunches were cooked on-site from ordinary ingredients, not microwaved ultra-processed garbage.
I have no idea how they will deal with this problem, but pretending all the "Snowfakes will toughen up" isn't a likely solution if they can't go on a 20-mile hike without breaking. Not everyone will, but there is already a problem with this, and that is with an all-volunteer service.
I can just see a "Karen" or "Ken" back talking a REAL D.I. 
And what about all those "helicopter" parents. They'll probably want to go to boot camp with their little tender babies.
