The optimal and frankly only solution would be the close the coal plant. Arguing that alternative solutions are not "optimal" while continuing burning coal is directly harmful to the environment, green politics and human health.

The first step would be the set a definitive date when the coal plant will get demolished. Once that is done, people can continue to debating what optimal alternative should be constructed but if the date come and there is nothing built then what people get is no power, and the blame then goes to those who refused to build new power plants when they knew ahead that the coal plant is getting demolished.

This is true. But there is the shortest term, say the 2030 goals (go full on wind and solar, there's still plenty of fossil base load that can be shaved off), and the 2050 plus subsequent goals. If we want to go full carbon negative (and we should), then nuclear is necessary.

Solar + battery is great but it isn't enough. India will be one of the worst affected by Climate Change. That would be nothing compared to the economic cost of Nuclear.

Nuclear should have been built and improved 30 years ago. By the time new nuclear plants bring about their benefits, we have passed the 2,5 degrees celsius warming limit.