It's a fact that white people will lose demographic majority status in the US next ~30 years - there's nothing conspiratorial in asserting this. The conspiracy (and opprobrium) come from believing it to be a (((scheme))) and a goal unto itself instead of seeing it as a byproduct of several cultural and demographic trends or policy decisions that were intended to be race-blind.
Even that though - is a lot to do with the very specific New World way that America tries to pigeon-hole and force racial categories. As in, there are a lot of American people who would be considered as being "white" elsewhere but who aren't in the American understanding of racial classifications; and the country is a very, very long way from having a majority of the population with no or little European ancestry.
In that case, the hand wringing over the dissapearance of a white majority is something that is mostly a question of definitions - or in other words, a reflection of the degree to which "race" is not actually a biological reality but a cultural one. Nor is one specific ethnic identity losing its status as the majority exactly a new phenomenon in the US. White Anglo-Saxons have long since ceased to be either a majority or even an especially identifiable population, in all likelihood the "Non-hispanic white" category will at some point go the same way.
In Europe it's even more so, I was reading something fairly recently on the demography of France, which is possibly the European country with the largest non-white population. In essence, if current rates of immigration and intermarriage continue, it will never have a majority with no "European" ancestry, or even with mostly non-European ancestry. And in any case, I don't really see why worrying about a country where most people have some North African or something background is on the whole any more worrying than the current situation where most people can probably identify some Italian/Portuguese/Polish ancestry. Demographic "replacement" as it is, is pretty much a constant phenomena across all of human history.
Which is all not to say that worrying about immigration makes someone a hopeless racist, more that pushing a "great replacement" narrative - even with the conspiratorial element removed - does play on some fairly racist tropes along the lines of "in order to be a genuine European you must have zero non-European ancestry and preferably not anything too close to the Meditteranean either"