China had ocean going vessels and they could've genocided Oceania and the pacific but they chose not to. The ottoman empire, while not perfect by any means, didn't engage in the same genocidal and slave owning campaigns Europeans did in the americas and Africa. It's not that empire or colonization are exclusively European phenomena, but European colonization was particularly cruel and extractive.

Besides, this is a non-materialist hypothetical. The reason we criticize the heritage of European colonialism and imperialism it's because we live in its wake. The wrongs of that past and the wealth created from exploitation need to be made right and repaired. If Ethiopians or Khmer had done the same and now were the hegemony sitting on mountains of stolen wealth, the criticism wouldn't change.

Saying "b-b-but someone else would've done it to me if I hadn't done it first!" is literally a point. And worthless in any conversation about european colonization.