There are a lot of things to look at, but you really do not have to look all day unless you are OCD about what you are doing every minute of your trip.
Ride times: I might check while waiting in line for another attraction or trying to decide which way to head in between. This might be a minute or two of checking at a time. I am not constantly checking times.
Dining reservations: I either make ahead of time or look when I finally decide if I want to see what might be available that day. I rarely spend more than 10 minutes during a day looking, if that.
Mobile Ordering: I think on my next trip this will be more in use than previous. Still, I can usually pick and order in about 10 minutes. It only takes this long because someone always changes their mind on an item before I place and I have to change.
Pictures: If I do not have my DSLR with me, this is where my phone gets the most use.
FP+: If/when it returns does tend to drag me in a bit. There were some days where it seemed like I was constantly on my phone for this, but that was usually if I was basically lucky enough to go from one FP line to the next. Over days/trips, I really just looked if I was interested in something or not and barely used.
Most of my other phone use is for non-WDW activities.