After a while, certain high usage routes will be noticed in the rideshare data. It will become obvious which streets and destinations could be optimally served with high capacity buses. Now is the time to bring in bus routes. Setup these bus routes and offer a discount for using them.
The current system isn't working, we need to try something different.
As far as I can tell many people are using public transport, including buses, so it seems to work to some extend.
You can't force a top-down solution for public transit with the road system in the US. The great strength of the US road system is point-to-point transportation. Let everyone benefit from that instead of running buses that only the poorest use. Publicly funded rideshare is the way to do this. After a while, the bus routes will naturally appear in the data. This is the bottom-up way to build a bus system.
Jarett Walker writes well about this coverage vs. ridership tradeoff: https://humantransit.org/2018/02/basics-the-ridership-covera...
And I know rideshare has a bad reputation because of Uber/Lyft. But government can create rules they must follow to accept these funds. They can either accept those rules or some other company will. Or maybe a government rideshare service is a better option. This is a classic free market vs government service question and there's many options here. But the important point is allowing everyone to use rideshare as a transportation option.
Probably what would happen is the busses would get shut down, the Ubers would be underfunded, then no new busses would be started.
Heck, the ridership on some extended bus lines is so bad and so expensive the city would have been much better off buying each person a small car and focusing the rest on more used lines.
Rail does much better because it's usually only built where it can be filled, and is electrified.
In the Netherlands we treat public transport as a basic necessity that should be available to everyone. Not everyone can own or drive a car (too old, too young, too poor, physically or mentally not able, hazard on the road for others), and you don’t want to force everyone to move to large cities where public transport is available: cities are more expensive. In addition, public transport usually has less impact on the environment.
Bussed are sized to need though: areas with lower demand are served by smaller, less frequent busses, or busses on demand. You need to call to reserve a ride. Which is almost like ride sharing, but not at the cost of ride sharing car owners.
Public transport has a large positive impact on a society, and as such doesn’t really need to make a profit. E.g., we all benefit if teachers that can’t afford to live in cites, can still travels into cities to teach children there. The entire society, including the economy, benefits from having the population educated well.