Not all colonialism is genocide, although most all colonialism that isnt genocide is also not far off from genocide and usually is a precursor step to it. Like genocide-lite

The colonization of a population by another power usually does not inherently involve mass murder of that population, the taking of their children, or explicit intent to wipe out their culture. Throughout history much colonialism has functioned through a process of the colonizer being a minority in the land of the colonized. Colonialism at its base is not something where the colonizer shows up to wipe people out and settle their own people in the same space.

Generally the way colonialism has functioned historically, at least simplified, is that the colonizing power shows up, denotes some specific segment of the population that agrees to take instruction from the colonizer as the upper class of society, and then enforces their rule (in as much as they can) via that hand-picked group. Sometimes prior to this you have missionaries showing up, whos goal also is obviously not one of genocide. Generally those who adopted the religion of the colonizer were those more likely to be hand selected as the upper caste that was favored by the colonizer.

Because colonial powers were often spread thin this is just the logical way that colonialism often functioned. Certain colonies ended up facing genocide once there was enough of a population that taking over land was considered a necessity by the colonizing power. At which point things tended to get far uglier