If I pull it out to read a book, I’ll treat my phone as if I’m reading a book and won’t care so much about how much “screen time” I have. Or if I’m using something like Instapaper. If I’m using Reddit, I’m looking for news on a specific thing or I’m looking for information on a topic, and Reddit is just one stop I make along the way, that doesn’t change whether I’m on my phone or laptop.
If I’m watching a movie or something in bed, then it is time I would have spent on a television screen anyway. If I’m taking notes, I’m taking notes. If I’m journaling, I’m journaling.
I’m not interested in how much time I spend on my phone specifically, I’m interested in knowing if I waste time. So far, I don’t feel like I waste time. My recreation time is well accounted for, and some of it is spent on my phone too, but I’m not against spending some of it on my phone.
At the end of the week when iOS 12 sends me a report on how I spent my time, I’m generally not surprise. If I am surprised, I try to be more conscientious going into the next week.
Both Android and iOS have gotten features to help curtail excessive phone use, which is a good first step. Something I do while I'm at work is put my phone in my drawer and in airplane mode.
The biggest pillar I'd like to see destroyed in modern tech (specifically wrt smartphone overuse) is advertising - the incentives are just so poisonous. Ads seem to be the driving force behind making certain apps, like instagram, as addictive as possible. A hard regulatory line needs to be drawn.