But the badness of the analogy highlights the flaw in reasoning.

They want to go to war with a simple design? Sure, they get a Lee-Enfield bolt action rifle. They fight against people with EF88 Austeyr.

They will die and lose the war.

Longer range, higher rate of fire, lighter, grenade launcher mount, scopes, more accurate, higher lethality, etc, etc.

Simple design so it doesnt't jam doesn't mean you've maximised all the other areas that are important for winning a war.

I fully agree with this. There is a reason long range sharp shooters use simple bolt action guns, while the vast majority of an army uses much more complex guns. A simple bolt action also happens to be the most precise gun we can make (a single shot musket would be simpler, but it wouldn't be more accurate and loading it would be a pain). You choose the best tool for the job. Properly cared for modern guns don't jam very often, and improperly cared for guns jam too often no matter how simple they are.