We solved these issues in the 19th century.
Our transportation problems are political, not technological problems. The problem is the lack of political will to fund and build public transportation and active transportation systems instead of continuously expanding the road network.
We already have several examples of how political problems can be hacked on and overcome. Uber's early days where they were busy opening up cities to the idea of a competing taxi service.
There's also the traditional way, activism. Activism seems to work best drumming up political support for social problems. Problems like this one tend to respond well to large sums of money collected to fund a trial run. Find just one city to try this out on.
Public transit's big problem is that it's been tried, and while it works, it requires huge amounts of political capital to be created and spent on each expansion of the transit network. A profit motive would allow this process to expand at the rate of demand.
But so far, transit is akin to utilities in that there's a real public interest in keeping prices down. Plus the transit agenda can get weirdly partisan. Here in Atlanta, the majority-white northern suburbs did not want MARTA train stations going too deeply northward. The pejorative expansion of the acronym was "Moving Africans rapidly through Atlanta."
So we need more Ubers in the world, companies that are not afraid to challenge political institutions in order to drive the public interest forward. The profit motive is needed in order to drive expansion, and the legal regime needs to be flexible enough to get around NIMBY naysayers.
There was a model that worked; transit has historically been used to allow property development. This was used in the development of London, Hong Kong, Tokyo, New York, and the multitudes of inner-ring streetcar suburbs in American metropolitan areas. The problem is that whereas Hong Kong and Tokyo held onto the properties, Western companies that used this model tended to just sell off the property, requiring Ponzi-scheme levels of land acquisition. That collapsed when they ran out of money and the federal government started building free interstates to goose the suburb-building instead. And now in 2018 there's very little cheap farmland within sane rail commuting distance of metro areas, and the model doesn't work in places like New York where a block of property acquisition is equivalent to building an entire train line. Even Tokyo has stopped building new railways using this model because it just does not scale.
And the model you list is still in use today, if you take into account that roads are also 'transit'. It's just not the kind of transit that you and I want to see implemented.
The eminent domain thing is a power of the state, but it's also true that even if you were to privatize railroads today, they could not afford to purchase all the required property for new lines at fair market value. Hence the dependence on the government to front that cost instead.
Subways are expensive to build, and expensive to maintain. If a technological solution makes implementing public transportation cheaper, I think that's a good thing
Edit: Also, Subways work well in dense city areas, but are less efficient is places like LA (outside of downtown) that are very spread out