On the topic of water/rain with a phone, reality is phones are increasingly waterproof anyways. My iPhone 11 is - rode several times in the rain with it last summer just after getting it and had no issues whatever even when it got directly rained on.
I enjoy far too many features of using a phone based navigation such as the traffic avoidance and LEO notifications in Waze, live road closure notifications, satellite view at times (IE is that a dirt road of a paved road?), free map updates almostly instantly vs manual updating a physical GPS at potentially significant cost, etc. Since most of us use our phones for music/audiobooks/podcasts while riding in addition to navigation, having it front and centre is just another layer of inconvenience.