As far as I know "casual games" are games that are very easy and very rewarding, thus great for pretty much everyone that just wants to pass some time (a huge audience obviously). This article somehow manages to use "casual games" as separate category besides, say, "Cards & Casino". What's the difference? Almost all games I've tried from the Play Store are casual games, even all racing and almost all arcade games, and I gave up on mobile gaming because of that.

It's not really about being in the charts, or even downloads, unless developers can make money from them. Unfortunately, there is more piracy on Android; ads can only bring in so much and break the experience of a game. Also, given the wide range in device performance, specs, and software, you really have to wonder if it's worth the time and money investment.

If this wasn't about mobile you would have almost definitely included more categories, which is the immediate problem with mobile.

the current game atmosphere really makes me sick. I don't know what it is about a casual game on a freemium model that is built to annoy you into reaching into your wallet that is so appealing to everyone.

You used to (and still do off mobile) buy a game in full and enjoy its lifetime value. I think mobile could be a great spot for more managerial type games, I used to love being the GM in many games

Yeah, but they are so much easier/cheaper to write and produce. 2D is par for the course for casual. Action and adventure much less so.