It’s really just comes down to thermal mass vs. power dissipation. Either you have to increase the thermal mass, or limit the power. 99.99..% of use cases are for the phone to be in your pocket inside, so designing in a larger thermal mass, or limiting performance isn’t going to be a factor that drives design.

However, since most phones are relative water resistant now, a good option is to use evaporative effects to cool them down. You could also dig a hole in the earth to find cooler temps and dissipate heat that way.