What's the most frustrating part of learning/practicing piano? Do any current apps actually solve it?

I've been playing piano for a while and lately I've been thinking about something: what are the things you struggle with the most when learning or practicing?

Second question: do you use any apps to help you? Do they actually work, or do you feel like something is always missing?

I'm asking because I feel like there are things no current tool solves well — but I want to know if that's just my experience or something more people relate to.