Ask HN: Which apps do you use, where you feel like the “primary audience”?

Do you feel you are the ideal user, primary user, etc for an app? In other words, you use everything about that app, anytime it adds a new feature you like and use the new feature, etc.

I'm primarily thinking about complex apps, not simple ones that have just a couple of uses. For example, Spotify. It does a lot more than just play music for you. But I can't imagine making use of, or even caring about, most of its other features. I can't think of a single app where I feel like the "ideal user". Wondering about others' experiences.