Your last four points are good, but in practice the first two have not netted significant advantages for NYC's bus operations: many of NYC's buses run on narrow

Your last four points are good, but in practice the first two have not netted significant advantages for NYC's bus operations: many of NYC's buses run on narrow one-lane streets, where any amount of double parking makes the road completely un-navigable. Similarly, it's more common to see a bus route taken out of operation entirely for a week than to have it re-routed on the fly (the latter does happen, but the network also dense enough where most riders can take the next avenue's route). I think a significant understated advantage to streetcars is their effect on local neighborhood development: like a subway line, a streetcar line is a semi-permanent installation that can't be easily taken away by a short-term replanning of the network. Bus lines, even when dense and well-developed (like NYC's are!), simply feel impermanent in a way that rail transport doesn't. (Or as another framing: if you build a rail connection to a neighborhood, there's a good chance there will still be a thriving neighborhood there in a century. It's not as easy to guarantee that with a bus route that can be taken away overnight.)