You make some good points. But...
Ride-sharing won’t be necessary.
Vehicles won’t need to be owned. And, the “rides” will be provided by fleet operators, but not by corporation such as Uber or Lyft. The fleet operators will be the carmakers themselves, since there won’t be any business needs for car dealers and manufacturers will have to operate their own vehicles in fleet formats in order to make up the difference in lost sales.
Vehicles will be summoned via phone or smartphones or PCs or even smart home assistants and perhaps smart TVs, and can be used on a scheduled basis, such as for a morning ride to work and afternoon ride back from work.
The whole autonomous vehicle future will be very disruptive, and it will affect car ownership (no longer available) and fuel-usage (much lower demand, if any), and cities and states and the whole country will have their complete roads and highways changed according to the needs and demands of vehicle usage. For example, no more parking lots, and no more parking garages at airports and no more home garages.
We’re in for a very disrupted future.
Apart from the ownership question (carmaker vs. corporation), what you are describing are essentially what we all know as taxicabs.
For better or worse, personal transportation will become a regulated public utility.
And what happens when an electric utility experiences a demand spike? Mostly they restrict delivery of their service (i.e. brown outs) as a better alternative to cutting service altogether.
In your scenario the same thing would happen. The scheduling computer recognizes that several people from a given area are simultaneously requesting transportation to a certain destination, and the computer also realizes that there aren’t enough available cars at that moment to give everyone a private ride. What happens then?
There may well be service contract levels such that for a lower cost, you might have to accept pooling at times, or for a greater cost, you might have a guarantee of private transit. Waiting time will surely be an issue, hopefully with discounts for long waits.
We will probably see the end of mass spectator events (sports and concerts). Malls are almost dead now, so they will disappear altogether. Most brick’n’mortar retail options will be gone.
As you say, the future is sure to be very disrupted.