I travel a lot. And one of the unsung features of the Starbucks app, is that the density of stores and the app means I'm never more than 15 minutes away from a consistent coffee experience.
I also did exactly what you were doing back in 2012ish. We even had an app. I thought preordering was going to be the next awesome thing.
It turns out that not waiting 5 minutes for your order kinda leaves out the whole experience of talking to the barista, getting that smile at 6am when you're not feeling it yourself, and the personal experience of the hand crafted beverage. My barista knows my name and my order.
And you know how often I use the mobile ordering feature of the Starbucks app? Like 3 times, and only when the line was really long.
Now if you wanted to create a niche market of curated handcrafted delicious coffee from friendly independent baristas, that's an app I might be more inclined to use.