You left out the poison pill of any type of public transportation these days: Cost
The public bureaucratic mentality is simply unable to cope with costs.
When "public" money is involved, no limits are seen to either employee demands or fare levels or using other related costs as a cash cows.
Of course neglecting normal highways and freeways is becoming increasingly transparent as an argument for a new limitlessly expensive public transportation system.
This is the only area on which we are in complete agreement. Once these systems were privately owned. Then a combination of unionization and the minimum wage made it uneconomical for private interests to run them. The unions learned to milk the systems because union members were voters.
I'd like to level the playing field and return to the days of private ownership. But that's going to require more political will than anybody has nowadays.