Here is the Reason.
1. first DF-21D is not ready yet, and tested once and that too a ground, static target.
2. It was developed by the China to deter the U.S/Nato carrier in South China Sea, and not for the Bay of Bengal because for targeting a carrier on the bay of Bengal you need the precise location from the satellite plus real time updates which requires lot of assets and equipment, which you have in the South China Sea, and is developing the web of around 40 Navigational satellite to detect and monitor the ships in the Sea on the western side of you border.
Apart from the Navigational Satellite, your assets such as SOSUN Network, and Ground radar station, and the long range Recce Aircraft are not deployed on the Indian Boarder, rather in south China Sea region.
Negative those are for the protection against the Brahmos type of Missile, and only Supersonic Missile could be intercepted, not the Hypersonic Missile, which DF-21D have the speed at its terminal stage, as claimed by the Chinese.
They cannot at the moment be realistic. And for that they have to invest at-least 20 Billion, if they wants.
I don't think so. Indian Navy have the experience of Carrier Operation for more than 40 years, and China is still learning that process. Second China lacks a carrier fighter plane, and the one J-15 have the problem of being underpower, so max it could be only used as A2A platform, with the current engine. On the Other hand, India have MIG-29K, an excellent platform, and most probably in future Rafale-M, Another advantage which Indian Navy enjoy is that it don't have the bad relationship with the powerful Navies like Japanese/S korean/vietnam/U.S/Nato/Taiwan Navy
DF-21D is operational
Tested on decommission Jianhu frigate! The news was not reported by US despite the whole process was watched by US satellite. The USN are too afraid to tell the world the success of DF-21D. The photo show impact without explosive warhead. Observe that the impact is from top rather than side of most sea skipping anti ship missile. Imagine a 200kg explosive warhead plus impact?