This is patently false. The PHB puts Halflings on par with Humans, Elves and Dwarves for how many adventurers are used. Further, it says this in Mordenkainen's...
"Some elders - especially those who once had fancy feet themselves- just shrug, smile, and say it is the way of things."
Fancy feet is the term for adventurers, so it is explicitly stating that there are retired adventurers in the village.
So... they have no more retired adventurers than any other place on the map. The same as the Humans, elves and dwarves...
How many of those places are completely safe from attack by monsters? How many times do you go to a town and find that the retired population of adventurers is more than sufficient to handle the nearby threats?
Also, holy selective reading Batman. You want to take that to mean that there are retired adventurers in every village? Let us look at some of the surrounding text.
See, the section you are pulling from is explicitly about adventurers, and it starts by telling us that the tendency to wander off is outgrown by "almost all children" the term fancy feet referring to the ones who don't outgrow it. Hmm, that seems to indicate a smaller bit of the population. Then, we get to the text talking about how each village handles it, where we get your line about "some elders" who had Fancy Feet themselves... Which is then followed by:
"Nevertheless, well-meaning villagers might try to dissuade a youngster from leaving the community. Other villages are much more supportive of one of their members who demonstrate the urge to adventure, likely because some of their their elders have gone into the world and returned to tell about it."
See, this text is kind of phrased in a way that is important. By saying "other villages" that implies more than one grouping, and what makes these villages unique are elders who left and came back. This, by quite literal definition, would mean that the flip side of that coin are villages whose elders didn't leave, or left and didn't come back. Meaning those villages don't have retired adventurers.
Which disproves your assertion that every single halfling village has a squad of retired, elderly adventurers ready to fight for their homes. Since the text tells us that not every village has retired adventurers in it. Also, here is a fun fact. I read through that section a few times. Know what I didn't see mention of? Magic and Weapons. Which was a rather important part of your claim.
It's literally listed under the goddess, and not where it talks about Halfling society above. It's her thing.
You mean the part I keep referencing? The one where you have these tactics:
Scatterstrike. The halflings run in every direction as if in a panic, but then they regroup and circle back to attack with a concentrated effort.
Turtle Shell. Halflings cluster together and cover each other with shields, washtubs, wheelbarrows, coffer lids, or anything else that can deflect a blow.
Troll Knocker. A few halflings act as bait to lure a troll or other large creature into a clearing where the rest of the group can
hurl stones at it from concealment to confuse the monster, persuading it to seek other prey.
Swarming Stickwhackers. Halflings rush an intruder in waves
, swatting the enemy with sticks on all sides.
Fiddle and Crack. A halfling fiddler lures the monster into a trap, usually a net or a pit, followed by several burly halflings
wielding large sticks and hitting the monster from a safe vantage.
These tactics, listed under the goddess, that mention rocks and sticks? The ones that don't mention any other weapons or tactics? These are the ones that tell us that they are going to use more than rocks and sticks? Where?
Who me one who said that Halflings are Marines who can't do any wrong.
See Max, I know how this is going to go already. Because you are obsessed with precise wording you are going to declare "Gotcha! They never said Marine!" while ignoring the larger point. I'm going to try anyways though, because I always hold out vain hopes.
Let us look at this from Doctorbadwolf
Also, halflings, unlike humans, wouldn’t run away in terror, they’d use hit and run tactics without giving in to fear.
Because people are really losing sight of how powerful Brave is as a racial trait, in terms of worldbuilding.
Halfling shield walls don’t fear the charge. Halfling cavalry don’t fear the wall.
Fear is a huge part of whether people survive danger, whether townsfolk repel bandits, etc.
A lower level fiend that could wipe out a human village will have a harder time with a halfling village because the halflings aren’t going to panic, and they are extremely unlikely to flub anything they try to do, which means they are more likely to try ballsy tactics, and less likely to have Hail Marys blow up in their faces.
Also, 5e totally misunderstands the lethality of slings, as a tangential note. A village where everyone is reasonably skilled with one and not afraid to use them in defense of thier town is a place where the incentive to raid needs to be much higher.
So, that bolded part is a claim that few things will go wrong. Not "extremely unlikely to flub anything they try to do" and "less likely to have Hail Marys blow up in their faces"
Also note how he mentions that a halfling village would be harder to wipe out than a human village, which actually has a trained guard with proper equipment. Note how he is talking about their shield walls being superior because they don't fear the charge, how their cavalry is superior because they don't fear the shield wall. This is implying they make far better quality soldiers than the other races.
So, I chose the term "Marine". High Quality soldiers, some of the toughest and deadliest, to represent this depiction. This idea that Haflings are simply superior warriors because of their innate bravery.
So, one person. You will declare "GOTCHA" because he didn't use the specific word Marine, and he didn't go all the way and claim that they would never once make a mistake, but I'm used to that by now.