The astonishing thing is that bandwidth isn't a big deal now, and we could have improved basically all aspects of mobile calls to be within spitting distance of what we used to have 30 years ago.
No wonder people don't like to talk on the phone any more.
Isn't that a little like saying "The only thing boats have over cars is that they can go on water. In all other ways they suck"? Portability is the entire point. Even in the "good old days" most people would have accepted nearly any tradeoff for the ability to carry even the simplest global communications device with them.
Originally POTS was circuit switched analog connection between you and the other party --- only delays from the wires, and maybe amplifiers. Nowadays POTS is most likely digitally sampled at the telco side, but each sample is sent individually --- there's no delay to get a large enough buffer to send, because for multiplexed lines each individual line is sampled at the same rate and a frame has one sample from each.