In short; you will need a working phone network to full explore and enjoy your trip.
I disagree - you do not need a working phone network. However, you do need access to cellular data (without wifi). That you can get either by using your phone's international plan or getting an eSIM data plan or a SIM card. So what company provides you cellular service?
If you have Verizon, they will charge you either $10 a day or $100 for the month. I used to have Verizon and opted for an eSIM data plan, which cost me $20 for 30 days of 10Gb. of data. Very easy to use and much cheaper than Verizon.
Now I have T-Mobile, which offers free international plans for its customers, including unlimited data. So I am opting for that for this upcoming trip.
But in short, I have been traveling for decades and have never once used my phone to call anyone. However, if you rely only on wifi, you will be somewhat hindered, which is why it would be smart to either get an eSIM data plan (which requires an unlocked phone) or use your cell phone carrier's international plan.