AxA has often been called a “beer and pretzels” wargame, I suppose because it is fairly simplistic and available—FOR a wargame. That’s not because AxA is elementary or easily mastered, its because other wargames tend to be even more rules-heavy and detailed, which makes some of them famously and notoriously unplayable. They may have an attractive theme or rules, but the “chit” game era (60s-80s) built up to a crescendo before it burst. PC Computer gaming was a major catalyst for this; the ASL/Avalon Hill/SSI style games BEGGED for a computer to handle some of the more complex calculations, setup, rules etc.
I think AxA has the general appeal and longevity it does precisely because it appeared after this “First Golden Age”, and is not married to overcomplex or overly realistic considerations, its a truly “abstract” wargame, where each step (building, conquering, purchasing, combat, movement) is fairly simple, but all together, they are complex enough to satisfy long-time players while only barely overwhelming the new ones.
And, the fact that AxA doesn’t try to simulate or do everything a wargame possibly COULD do is the very reason why there is enough room left in the game to add more, but that’s not necessarily desirable. If the game was already highly complex, rich and random, it would already have many of the things that people are trying to add to it—but its likely no-one would play it. I think most of the more complex house rules systems for AxA fall into this trap, by pushing the complexity/time investment level out of the Goldilocks zone.
I bought a “political” Avalon Hill chit game in 1992, Republic of Rome (4/4 difficulty rating). When I read the instruction manual, I was blown away-- I understood nothing of what i’d read… until I read it for nearly 2 years. We only played it in college 4 times, and the Republic consistently lost as a group. Its a great game, but its also an example of a highly complex simulation game with a narrow audience from the first era–very few people still play these games because they lack any general following or appeal in the internet age, and have been replaced by computer-style games, like the Total War and Europa Universalis series.