The referendums are deemed by the United Nations to have been organized in violation of the United Nations Charter and to be illegal under international law. Here's the response from The White House:
Statement from President Biden on Russia’s Attempts to Annex Ukrainian Territory
China, India and Brazil abstained. That's a large percentage of the world population.
When Western puppet politicians and media talking heads speak of "world opinion", it's generally just western countries and vassal states that are militarily occupied