You might want to try Reset Network Settings before you make a decision on that, or even Reset All Settings. Be a shame to erase it before resale only to find there was nothing wrong with it.I have a XS Max, planning on upgrading to the 15 pro. Potentially the 14 if I think USB-C will be too much of a hassle.
Phone is in great shape, just the comms are terrible. LTE disconnects constantly, wifi is up and down. Nothing wrong with the processor or screen, it’s the “internet communication device“ aspect that is failing.