Have found my phones to be a very mixed bag WRT replacing a dedicated GPS. Am sure that the specific model makes a big difference so can only address ones I've owned:

It can be a challenge shutting everything down except GPS and the map app. If the phone is roaming, looking for a signal it will eat up the battery with blazing speed.

Downloading basemaps and/or sat imagery to the phone ahead of time is fraught. Some apps will not let me access my map cache if I'm not on a network. Research this carefully.

Can you preprogram waypoints, junctions, campsites etc. ahead of time? Can you reliably retrieve them?

My phone GPS chip and antenna have never approached a dedicated GPS in signal acquisition and speed. In sketchy surroundings like heavy forest, steep hillsides, canyons, etc. a signal can be hard or impossible to acquire. Since the phone combines cell tower signals and GPS service in normal use, test yours with wifi and cell service shut off and see how it does with just GPS.

On the plus side, phone displays are miles better than GPS screens and I have found with my integrated PV panel-battery I can recharge my phone (and other items like headlamp) to keep it going indefinitely.

In sum--research each link in the GPS and map chain carefully before deciding "my phone will be plenty." I'm not there, not yet anyway.

Cheers,