BART was getting very crappy when I used to ride it into the City from Walnut Creek every day fifteen years ago - I can only imagine how much worse it is today. There seems to be almost no way for the system to make money if the nearly insatiable commuter demand of two decades ago is becoming a thing of the past. It will just be another permanent government giveaway like Phoenix light rail - a rolling homeless shelter offering nice contractor kickbacks to Democrat politicians.
The San Diego light rail system had good ridership when I was last in California about 12 years ago.
Perhaps the Phoenix heat is too much or the Phoenix area is spread out too much for light rail.