Mobile, rpg, "clash of clans", rip-off games are just not good

Is it just me? or is there an entire list of mobile rpg strategy games in the android playstore? That consists of pretty much half of all the applications there? Is this a simple trick for videogame developers to just throw away games in the playstore? There's absolutely no way that almost all developers tend to create these kinds of games, there surely must be some easy method they use to create so many strategy mobile games. I have seen ads about mobile royale, many ads. And the game simply doesn't look like anything impressive.