I agree with the philosophy of "do one thing, do it well", but my problem with a lot of app ideas is that they focus on adding one feature to an existing app. I dislike this because then I have to switch accounts just for one extra feature. Instead, I think there should be a focus on providing one value in a product. It should solve one problem, and solve it really well. That means defining and scoping the problem in real life terms. The difference is you might need to write several features in order to have the perfect workflow.