A hitman would share that opinion, true, because he's not a soldier. A hitman is a civilian that only has to take one shot and can generally set that shot up as much as he wants to, so all he'd be concerned about is if that one shot would be enough.
A soldier, especially one focused on fighting and winning wars, has one primary hostile to fight, which is called kilograms. I was trained on the G36 and it weighs depending on what gear you strap to it and how full your mag is between 3 and 4 kg.
Standard battle-rattle is four extra mags in single mag pouches around your body, however you distribute it. That's 4x30 + 1x30 in the gun, which means 150 shots on you. That's not much. And yet, it adds up to 5kg.
So you have a gun and barely 150 rounds for it
-and with just this pathetic load are already dragging around 10kg with you. Just on the gun and no further equip for battle.
If I was in the army here 20 years ago they'd have given me a G3 which is what the CETME wishes it'd be. The loadout was different- the G3 weighs fucking 5,5 kilos loaded. I'd still have gotten 4 extra mags, but they only hold 20 shots now, but are heavier. So only 5x20 = 100 rounds. And that loadout is almost 15kg. That's no good.
1st Lieutenant (later promoted to Field Marshal) Erwin Rommel ("desert fox") wrote in 1915 during the offensive against the French close to the Ardennes, a fight that due to the terrain (standard european dense forest) meant engagement ranges less than 100m and often less than 50m that the one side will succeed that shoots first and keeps shooting with the largest amount of fire on target as possible. ESPECIALLY when suddenly fired upon from unforseen angle, the correct solution is to immediately turn towards them and hose them with everything you got. He proceeded to implement this by carrying the heavy machine guns (MG08/15 type watercooled tripodded beasts, and absolute PAIN to lug around) in the first row of the riflemen and immediately deploying them and hosing whatever was shooting at them if they were suddenly engaged. This immediately suppressed the hostiles and allowed the rest of his forces to engage them from the flanks, thus defeat them.
This is of curse the crudest fix for his problem imaginable, but it was the fix that he had at hand in the time frame. Nowadays with out leisure of modern technology, we can approach the issue much better. My point is, for tactical engagements with other troops in the picture, large amounts of ammo and ease of carrying it with you and capability to rapidly deploy it at the spotted enemy is absolutely vital. Not BIG BANG BOOM HNNG HIP THRUST OH NURSE PLEASE MORE RITALIN.
For a real soldier, actually killing the enemy is almost a secondary objective. Much more important is not getting killed by the enemy, getting wherever you're supposed to be quickly and unharmed and without obliterating your knees carrying ridiculous loadouts AND UNSPOTTED, spotting the enemy in turn and reporting to your superiors the location of the enemy. If you have done all of these things, the enemy might as well be dead. If not by you, then by a swiftly following air strike or artillery shelling, or perhaps command will, in its infinite wisdom, decide that a well known and observed enemy can simply be entirely bypassed to BLITZKRIEG harder into the rear of the enemy held territory to fuck things up over there.
What I'm saying is, if you think being a soldier is about choosing the gun that makes the enemy explode into the most finely-misted giblets then you're a retard. I'd rather go to war with an entrenching tool I sharpened on a rock and a G36 that's been modified to only be capable of firing BLANK ROUNDS or fucking explode in my hands as long as I'd get working radios, NVGs, binocs, good bad weather gear, good boots, a functional supply situation and reliable artillery backup. Even if they'd cast me into the assault infantry role, I'd still do it. Because this is all much more important than my shitty handgun.