All of the linked apps look trivial to me. Also, the first one, the UI has no feedback once you click the answer (plus some questions don't really make sense as they have the answer in them). There is more on the website, so there could be something interesting, but I'm having trouble finding it among all the noise. Not saying simple apps have no value. Even simple throwaway UIs can have value, especially if you develop them quickly.

How about these ones, are these trivial too? https://news.ycombinator.com/item?id=46582192