In the U.S., the decision to go to war is made by civilians: the President and (ideally) Congress. Below the President, the top military decision-maker/administrator -- Secretary of Defense -- is also a civilian. All the people in the country could sign up and join the military and yet have no authority to actually go to war.
But I'm not naive: the decision to go to war is made easier when the commander-in-chief has a capable and willing army to command. I teach a programming class and I like to talk about "real world" algorithms, such as the Vietnam War draft and lottery [0], a tragicomical example of how hard it is to generate random numbers. But the algorithmic thinking is not just the details of the lottery, but why the lottery was the needed algorithm in the first place. The answer: because not enough people want to volunteer for war. And random selection seems to be the only way to raise an army without angering the citizenry.
Now that we have a volunteer army, there are new algorithms in play. Such as where to focus recruitment efforts based on demographic makeup of people who currently volunteer. This is all to say that as bad as the draft was, a volunteer army doesn't make things hunky dory. And why should we settle for anything less than the quip, "What if they gave a war and nobody came"?
So yeah, I see the rationale for not making the military easy to join. OTOH, I still think that the prospect of war -- and the use of military force in matters of diplomacy -- is a reality we have to live in. Making the military more smoothly administered does not necessarily correlate with an increase in horrors of war. If the military attracts good people, then that means there is the chance of having good people in the chain of command.
To go off on a tangent, better military technology hasn't always resulted in more war. The atomic bomb was used to wreak horror; on the other hand, the prospect of nuclear war seems to have stifled the kind of "great" wars we've had since Hiroshima.
So to answer your question: I think it's too simplistic to think of a better military as being a net negative, if we accept the realities of the current world.