HOWEVER the main problem (apart from just not having service) is congestion. There is a complete shortage of low bandwidth spectrum which can penetrate walls well in (sub)urban areas, at ~600-900MHz. Most networks have managed to add enough capacity in the mid/upper bands to avoid horrendous congestion, but (eg) 3.5GHz does not penetrate buildings well at all.
This means it is very common to walk into a building and go from 100meg++ speeds on 5G to dropping down to 5G on 700MHz which is so congested that you are looking at 500kbit/sec on a good day.
Annoyingly phone OSs haven't got with the times yet. And just display signal quality for the bars. Which will usually be excellent. It really needs to also have a congestion indicator (could be based on how long your device is waiting for a transmission slot for example).