I wouldn't worry too much about it, as long as you take some precautions. Namely having an exhaust vent running to keep stream from accumulating as bad, not running water so hot you turn into a lobster, and keeping your phone on a low shelf below the majority of the steam.
This won't make your phone 100% safe, but it's what I do with my non-water resistant V20 and haven't had any problems with it. I would not take it into the shower itself, or have it in the bathroom if you don't have an exhaust vent and have very hot water. If you're wanting to listen to music, just get a cheap Bluetooth shower speaker. Much better sounding and you can leave your phone further away/outside the bathroom. This is the one I have and it sounds pretty good for its size and price.
https://www.amazon.com/gp/aw/d/B01FX...cUvbUpU6319888