That is precisely the issue that I have been trying to explain to the Chinese fanboys here -- That absent any credible testing regime and that the results of those tests are presented without conditions, we do not know anything other than the fact that there are considerable technical problems involving hitting a moving target, even one moving as little as 30kts/hr.
But if China succeed in producing such a weapon, not only India but any navy that wields any ship, never mind an aircraft carrier, is seriously placed at a disadvantaged. The 'aircraft carrier' bit is really irrelevant as far as the technical aspects goes. If the DF-21 is proven to be a viable anti-ship ballistic missile, and proven mean beyond Photochop, then all ships, not just aircraft carriers, are at risk.