People don't like games like Flappy or Angry Birds for essentially one reason: they're afraid that these games represent the future of gaming.
We're told over and over again that mobile gaming and tablet gaming is the wave of the future and that the AAA model is unsustainable. We're told this not just from harmless nobodies, but by prominent individuals within the industry weighing in and being quoted in articles. People aren't mad at the Flappy Birds creator per se, nor even at the game itself.
They're mad at what they perceive as the slow road towards their own gaming preferences becoming niche or underserviced markets. It's why some RPG gamers *cough* get mad at MMORPGs being made in place of traditional RPGs.
Anger is often just a cover for fear. I'll own up to it. I don't like games like Flappy Birds specifically because I find them dull and unentertaining, but I also see how many developers and publishers have been pushing to capture the casual market in recent years, often at the extent of more "core" gamers.
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