How much time do you spend on your phone each day?

The problem isn't your phone. The problem is you are a monkey that has been given a window into a world with an endless supply of the things that primates like. I would advise meditating for 20 minutes every day. It won't solve your problem but it will help you control it.

I also spend hours a day on my phone. Mostly in the evenings, but also during the day.

My childhood memories are my dad either sitting at the kitchen table and reading a newspaper, or him lying in bed reading Dick Francis.

It's the same thing basically. Human minds like cheap distractions, especially if there are no other urgent things to do.

At a superficial level it seems like a flaw ("There must be more productive ways to spend the time"), but I'm sure there's an evolutinary reason why we are like that.

Maybe these distractions are a way to prevent us from overworking, because mindlessly reading stuff is a lot less exhausting than doing something productive for 14 hours a day. Maybe it's a way for our body to rest when we're not ready to sleep yet, or something.

I use phone for 3 hours/day and I'm now on the progress to reduce time spending on phone by have more workout activities, find a remote job. You can also try to find a new hobby such as cooking, reading, or maybe listening to a podcast.

Well, let's see. I currently work remotely and have 3-5 hours of meeting per day. So I'd say I spend about 5 hours on my phone.

0-5 minutes a day.

i refuse to look at my phone when waiting in line etc.

i meditate instead. does wonders for mental discipline.