@thor
Not just you expected but Mumbai do it self needs a more dense network which is much more bigger to solve the crowdings. Also the Mumbai metro and monorail have just started in 2018 and they would be expanded to cover the isolared pockets.
At the end the problem with Mumbai remains that it is very very densely populated (2nd most densely populated on earth) city which is surrounded by the sea on three sides so not much room to expand. Hence it is hard to build anything in Mumbai.