Both can be (and are) true, while the Europeans and later Americans did many things that would now be classified as genocide and ethnic cleansing, the majority of the native population simply died inadvertently of diseases. It’s actually unlikely that the Europeans would have been able to so thoroughly conquer the Americas if the native population would have survived the first wave of diseases.
If the only alternative to the failing status quo is the far right then we are doomed. Keir Starmer is not a beacon of hope, he is a pause button on worse to come.