Player Research founder Graham McAllister, gave a talk at Pocket Gamer Connects San Francisco 2015 about how researching the user experience can help improve user acquisition.
He warned that "you will not buy your way to the top", and that app stores are now looking to feature games that are high quality, rather than with high UA budgets.
You can't please everyone
McAllister also said that "a lot of companies are very bad at analysing their competition", as they look more at what the other games are doing, and not at how users are responding to this.
However, he does warn that your game will mostly like have some feature that doesn't gel with users, and "a significant number of players will leave for that reason" alone.
For that reason, you need to make sure that every single aspect of your game is high quality to retain users.
You can see all our videos from Pocket Gamer Connects San Francisco 2015 in this YouTube Playlist.