I'll go out on a limb here and answer the question asked above; why is AOS so unpopular?
I would say first that I don't believe that AOS is nearly as unpopular as it has been portrayed. I think that notion is skewed because it has been so roundly rejected by practically the entire Warhammer tournament community. The people who are enjoying AOS are not 13 year olds who decide games by throwing miniatures across the room at each other and fist fighting over the results.
Even though GW has been attempting marketing AOS towards a younger audience as they do 40k, the true core players who have been with wargaming all their adult lives have been coming back to fantasy because of AOS. In addition, many long-time immersive and story-driven players of Warhammer and GW games have moved to AOS as the newest game.
The competitive community underestimates the sheer number of private Warhammer players there are out there, as well as the sheer number of people out there who primarily buy GW stuff for the modelling and painting hobby aspects of Warhammer and not the gaming aspects.
I have a belief that for much of the fantasy wargaming society, there is an imagination that is sometimes, often times lacking. Here me out. What I mean is that even players who value quality paint jobs and quality games don't ever REALLY TRULY immerse themselves in the genuine roleplaying spirit of the game. It's still about being the best and knowing the stats better and mastering all the thousand stat. nuances that have nothing to do with the world or the atmosphere the game is supposed to take place in.
With the new gamer-developed "9th Age", an attempt by competitive Warhammer players to create a new, better, "balanced and more competitive" 8th Edition of Warhammer, it's still really all about the obsession with the idea that the ONLY time a game can have true depth is when it's so hard to learn and it's so heavily laden with stats and counter-stats that only the "true general" and the "true genius" can play it well – well I'm sorry, but that has more to do with human ego and humans needing to feel accomplished and superior than it does having a quality gaming experience.
AOS – at it's heart – is about two players sitting down to tell a story. Pure and simple. And, despite the insistence of competitive players – Warhammer 1st-8th was also about two players sitting down to tell a story. Nothing more. The "competitive" aspect of a fantasy game like this comes not in being able to know your opponent's roster in your sleep and knowing how to deploy so that you've won before the game even begins – the competitive aspect comes from allowing BOTH your strengths AND weaknesses to show on the battlefield, and then you just go at each other and let the dice fall where they may!!
But this insidious notion of what is a unit's "best and ultimate application", or what is the "best application for which unit in which situation". How is that a realistic simulation of war? No surprise, no shock, no spontaneity, no immersion, no NOTHING. When a game is boiled down to the stats with the miniatures as a backdrop, then that game is LOST. And that game is also confined to whatever official rules GW releases – hence, the competitive community screaming foul when a so-called "unbalanced" army book is released – I still laugh at the competitive community outrage over the release of the now infamous Skaven army book for 8th edition – while all the while all competitive Skaven players gleefully rubbed their hands. You just had to roll your eyes at the wasted energy.
I mean it's all NONSENSE. And I've never had any patience for it.
That is why I, as a Warhammer player of 20+ years, have never once attended a tournament, as have none of my gaming group. We play Warhammer and AOS to enjoy an INTERACTIVE STORY – a story told through a miniature battlefield.
If you think what I'm saying is overly dramatic and exaggerated, I would simply like to use two examples of how a competitive battle report compares to a story-driven battle report.
Look, I realize that everyone plays a game for different reasons, and great, to each his own. But this isn't about that – this is about rejecting a game because of its supposed "lack of depth" and "lack of "decision making" that the competitive community so badly needs in order to feel like it's playing a "real" game. I would say that the competitive community misses out on all the best aspects of what a game like AOS has to offer. To me, playing Warhammer competitively is like taking a classic novel like The Hobbit and only reading its summary. You're missing out on 95% of the experience, pure and simple.
YOU decide for yourselves which one of these you would rather read if it was put into a storybook form, and which one engages your imagination more. Personally I find the contrast to be astonishingly striking;
From the Youtube Channel "Follow Furion", a hyper-competitive Warhammer player(is this a Warhammer battle report or a financial spreadsheet analysis, OMG???);
YouTube link
And now from Pictors Studio, an AOS player who does story-driven battle reports as MongooseMatt does;
TMP link
***This to me is NOT merely "two different styles of play" – this to me is an example of a game that has had the life totally sucked out of it – and another example of how a game was always intended to be played. Seriously.