One of the problems facing military force planners and doctrine writers is that they have to do most of their planning in peacetime when they can't test their musings against reality.
This drawback is inescapable, although there's reason to think modern simulation techniques and realistic training can mitigate it. Still, military planners in the interwar period were faced with an especially challenging environment. Military technology was developing at an exceptionally rapid pace for peacetime in the 1930s (less so in the 20s because there was a surplus of Great War equipment lying around and other factors slowing things down such as naval treaties and Versailles.)
So it's not surprising that there were a lot of things that sounded good on paper in the writings of military experts in the 20s and 30s that turned out to be wrong in the light of actual combat experience in World War II.
For example, what's the best way to field tanks. After World War II the major powers have settled on the Main Battle Tank idea, which is that the only tank worth the trouble is one that is powerful enough to fight other tanks, mobile enough to exploit its own breakthroughs and cheap enough to field in adequate numbers. Modern armies have a number of specialized lighter vehicles for recon, infantry transport and mobile artillery support, but they generally have just one kind of tank (although they may still field a previous generation of MBT as well).
The British, no slouches in tank thought between the wars, thought there should be a functional divide between heavily armored, but slow "Infantry" tanks and fast, but lightly armored "cruiser" tanks. Unfortunately they compromised the experiment a bit by having inadequate firepower for either, but even improved firepower in later models didn't save the concept. The French followed a similar idea.
Most of the other powers went more with a light-medium-heavy division for their tank arms. This worked better than the infantry-cruiser division of labor, but also eventually fell out of favor too as it was found that light and heavy tanks were just as much trouble as medium tanks but nowhere near as flexible.
One further notion that was already falling out of favor even before the war got going in earnest as the "tankette." All the major armored powers has already decided the concept was unworkable, but tankettes saw combat with some of the second-line armored powers such as Italy and Japan and with minor armies such as Poland. The idea was that swarms of highly mobile, 2-man tankettes with machine guns would overwhelm the enemy. It turned out that the logistic cost of the tankettes did not justify their limited combat power. And they were vulnerable to a wide variety of weapons. Anything that could kill a tank could kill them, as well as many weapons that were not powerful enough to kill a tank.
It was a cute idea, but simply didn't work. The attractiveness of the concept is illustrated by the appearance of the AT-ST "chicken walker" in the Star Wars universe, which is again a small, fast, 2-man fighting vehicle not unlike a tankette in concept. Of course, in a fictional universe anything can happen, and whatever tactical drawbacks the AT-ST might have (and they do seem to take heavy losses) are not necessarily reflected in the scripted outcomes.
But in the real-life crucible of World War II the idea was discarded.
Tankettes do not appear in large numbers in wargames, but in those games where they do appear, such as Advanced Squad Leader and Axis & Allies Miniatures they are not especially useful.