You don’t seem to have any faith that people can learn new skills to meet the changing demands. Why not?
Raising a family ties people down. If it’s a contest between a set of people whose primary occupation is raising families and another set of people with killing and looting as their mode of existence with either group having access to the latest weapons (the latter, in fact, able to afford more for weapons because these are their primary tools) the latter will always win. There’s a limit to how much resources a person can dedicate, if he or she also has family to take care of. Increasing these resources requires large scale pooling, which inevitably leads to government. The farmer’s taxes go into funding the army that’ll protect his property from enemies afar.