This is something they could be doing better, but automobiles are just inherently problematic. Adding more of them demonstrates the fact. On a rail line that can handle the same number of people, you have lots of room for more cars. The cars are truly awful in every major city. They take up a terrible amount of room and even modern ones produce a lot of pollution.
(We've discussed here in the past that gasoline vehicles produce a lot of unacknowledged PM2.5 and smaller soot which is simply not found by typically used means because the bulk of it is smaller than can conveniently be detected, but I'm having trouble finding the article now due to ongoing enshittification at Google.)
The fact that adding a really frankly small percentage of additional cars can cause so many problems is an indictment against any idea which involves more of them. SF tries to solve its transport problems with buses, but its multitude of narrow and twisting streets designed to wend their way over and through the hills make that impractical for many neighborhoods. The result is that a trip that's 15 minutes by car or an hour on foot can become an hour and a half by non-car public transit because there's no convenient way to get a vehicle that large from point A to point B. I lived in Bernal Heights and worked at the foot of Potrero Hill, and I had to take a bus to get to rail to get to a bus in order to commute by MUNI. But if you ran an elevated PRT line more or less straight there, it would get you there in five minutes or so.
Alas, we let the greediest and most ruthless people run off with the money, so we can't have nice things. We clearly have the technology.