Big supporter of public transit, but this is apples to oranges. Nine times out of ten, the Uber is going to get you where you want to go a lot faster, unless embarkation and destination are both on the same public transit line.
I lived carfree in Milwaukee for a while (picking that as an example of a city that only has bus service), and the time savings really didn't seem that bad once I got used to it. A trip to one of the shopping malls on my side of town was about the worst-case scenario, and there it typically took ~40m on the bus, versus ~20m by car. I like reading and I had a Nintendo DS at the time, so that ~20m difference was spent doing what I would have probably done with the extra time, anyway. I was just doing it without a cat in my lap.
An easy trade, I thought, considering that I was typically spending no more than $10 a week on bus fare. Often more like $0, especially in the summer, when it was more fun to get around by bike. Owning a car or using a taxi service for my main way of getting around would have cost thousands per month. That's quite a few fewer apples, and not a whole lot more oranges.
We technically have a bus system, but it’s a joke.