I got an iPhone 12 about a month ago in the US, and noticed my town has 5g. My town is < 1 square mile, and a population of just 600, so I fired up a speedtest and was astounded... I was getting 560kbps, at 6am, on a Saturday.
It is actually very difficult to even send iMessages at those speeds, and forget about sending a photo to someone. If I'm not on my wifi at home, my phone is almost useless as anything but a phone.
T-Mobile is in a similar boat as they have a narrow chunk of 600Mhz dedicated to 5G service, but they own a bunch of spectrum right above 2.4Ghz WiFi (usable with much more powerful radios) that should enable 1100Mbps speeds and higher, but it will take another year or two to see it widely deployed.
My sister in law has AT&T, and her boyfriend has T-Mobile. So we are a full spectrum of the American cellular network. We all get full bars of "signal" while outside, but Verizon is the only one (4g or 5g) that will actually connect to the internet to do a speedtest.
Everyone in town just chalks it up to that is the way it goes, but worse than that, we only have one internet provider in our area, and from Christmas to New Year, we had a total of 50 hours without internet.
We live in a tiny tourist town that is a 45 minute express train ride to/from NYC, and while we may be close in travel, we are very distant in our available amenities.
It is actually very difficult to even send iMessages at those speeds, and forget about sending a photo to someone. If I'm not on my wifi at home, my phone is almost useless as anything but a phone.