It’s not supposed to replace your phone. With my watch I get motivated to exercise because I want to close the circles, it helps me sleep tracking, helps me get reminders to take vitamins, and I can look and quickly respond to notifications without having to take the phone out of my pocket or pick my phone up.
Also when I’m exercising I have full control of the songs playing or the podcasts I’m listening to without handling my phone at all.
Plus it can serve as a dashboard to take a quick glimpse of how your day is going, depending on the watch face you use. Weather info, exercise info, calendar info, etc.