On the first look app design seems not to be really appealing for an UX Designer. Your interactions and your technologies are limited. Most Apps follow the same structure and use the same patterns.
But App design is the most educational field an UX Designer can explore. No other interactive product is so often used as an app. No other interactive product is so integrated in our daily life. No other product has a higher expectation to be instantly understood without a manual.
Everybody can develop an app, but it needs the right set of qualified people to produce it, to develop it further, and make it successful – for a constantly changing world.