First, Russia never sought to side-line India on the Afghan talks that it’s hosted over the years. In fact, it always invited India to participate on an equal standing with every other party but New Delhi declined to do so. The Hindustan Times quoted the External Affairs Ministry spokesman in November 2018 to report that “India to be in talks with Taliban in Russia at ‘non-official’ level, meeting to be held today”. This was presumably influenced by India’s interests in not doing anything that could legitimise the Taliban’s political role in the peace process while still retaining a seat at the table in a non-official observer capacity. It was entirely New Delhi’s decision.
Second, Russia has come to realise per the established precedent above that India has no desire to seriously participate in Moscow’s Afghan peace process. If the Eurasian Great Power wants its proposed talks to achieve anything of tangible significance, then it would make sense to only invite serious parties, which India clearly isn’t because it only sent “non-official” representatives to earlier events. Even so, India could probably still join the process if it finally decided to dispatch official representatives because it’s extremely unlikely that Russia would reject its participation in that scenario. After all, Russia and India are trusted strategic partners.