Not just tech advances, though that’s part of it. The Army operates on the concept of “mission command” which basically means everyone down to the lowest private understands the essentials of the mission and can act to further the objective in the absence of guidance. We need *smart* Soldiers.
One thing I love about the myths the military tells itself is about its professional discipline, when in reality what the nazis hated about fighting is was that we didn’t follow our own doctrines and so they couldn’t predict what we were going to do on the battlefield.
Like, find me any career field that wants its ranks filled with stupid people. I’ll take a smart custodian to mop over someone who is stupid, because if they’re stupid I’ve got to spend precious time holding their hand on everything.
I don’t think there was a time after Frederick the Great, when soldier=brainless automaton was an ideal that any country wanting a strong military strived for.
This is what I've heard from people in a position to know. I have no first-hand experience. My uncle fought in Vietnam and I was reflexively anti-military. But things are rarely as simple as we'd like to think. I guess it comforts people to write groups off as evil, but it's actually not productive.