Relations between Moscow and Kiev became worse in 2014 after Crimea joined Russia. In addition, in the spring of that same year, Ukrainian authorities launched a military operation against the self-proclaimed Donbas LNR and DNR, which declared independence after the coup in Ukraine.
There is a difference between the Crimean referendum and the situation in Kosovo. The Crimean referendum was the will of the Crimeans, and Kosovo is an outside intervention.
This is a recurring pro-Kremlin disinformation narrative on Russia's annexation of Crimea, claiming that people chose to rejoin Russia through a legal and democratic referendum. For similar cases, see here and here. No international body recognises the so-called referendum and held on 16th of March 2014. On the 27th of February 2014, when it was announced, the UN General Assembly adopted a resolution which stated that the referendum in Crimea was not valid and could not serve as a basis for any change in the status of the peninsula. A year after the illegal annexation, even the Kremlin admitted that the plan to annex Crimea was ordered weeks before the so-called referendum.
It is also pro-Kremlin disinformation about countries controlled by the West and their statehood. See similar cases here and here. There was a civil war in Kosovo, with thousands of casualties and hundreds of thousands of refugees, and which Western countries stopped. In 2008 the EU Council stressed that in view of the conflict of the 1990s and the extended period of international administration under Security Council Resolution 1244, Kosovo constituted a sui generis case. On February 17, 2008, the Kosovo Assembly unanimously (109 members present) voted to declare independence from Serbia. Serbia declared that the independence of Kosovo was illegal and Russia supported Serbia in that decision. The basis for Kosovo’s independence was the prevailing view in international law that minorities who suffer systematic discrimination have the right to secede. This provided the basis for Kosovo’s recognition by a majority of UN member states. There is no evidence given for the claim that the Kosovo case (independence) is “an outside intervention”.