Answering the question of whether or not the Ganga Action Plan was successful depends really on what sort of perspective you are looking at the problem from.
With respect to raising awareness about the pollution and problems that the Ganges is currently suffering from, I would say the plan was successful in helping to draw people's attention to how much pollution is actually entering the water. Even though there was pushback with some of the initiatives, it sounded as if there was at least a recognition that there are problems with the river. In regards to actually curbing and controlling pollution, while also limiting infectious disease spread, I would say the plan has failed. There was never any real focus on curbing infectious disease transmission, with efforts instead trying to control main pollution distribution pathways. In regards actually cleaning up pollution, the wastewater treatment plants and other measures were not able to function at capacity and were even unable to run at all during monsoon season or during electrical outages. If the goal is to successfully remove pollution and wastes from the river, methods of pollution control need to work correctly.
In summary, there were some components of the plan that were successful, but others can be decisively be referred to as failures. In my opinion, the small gains made by the project were far outweighed by the failures to address key problems. Therefore, I would consider the overall Ganga Plan a failure.