I'm not sure this is a really fair appraisal of Cook.
Perhaps others are more knowledgeable than myself and can correct me, but my understanding is that Cook was more of an intrepid explorer and respected commander than a "colonizer".
For example, Cook is kind of credited with the discovery of Australia but that's not really what happened. The dutch knew that Van Diemens land existed for ages but no one was interested. Eventually when the English were looking for places to colonize so they sent Joseph (Joey) Banks who was kind of a rock star level celebrity naturalist to claim Australia, and Cook steered the ship for him.
It was Banks that returned to England and declared Australia to be "terra nullis" as in he falsely (fraudulently?) asserted that the land is free to be claimed because nobody has established use or control of the land.
It sounds like Cook took more effort than most captains to support good relations with natives on the various islands he visited. This wasn't altruistic, as ships often needed to resupply and what have you, but then there's resupply and there's "resupply" I guess.
Cook is well known for avoiding any kind of inappropriate personal liaisons with native women which was not the norm for this era. Relationships that we would describe as prostitution were normalised. Oddly enough the currency exchanged was usually nails, as islanders couldn't forge steel but nails could be sharpened into great knives far superior to anything you can make from bone.
Cook certainly wasn't in Hawaii to colonize them. IIRC they revered him as a god but something happened during a visit that betrayed him as a mortal (or something?) and the natives were angry at being tricked. IDK. Google it, but they didn't murder him because he was trying to colonize them.
It's hard to describe someone who lived 250 years ago as "good" or "bad" because it was literally a different era with different societal norms. However, if someone flew to Mars and planted a flag there you'd kinda have to respect that achievement even if they're not someone you'd like or really get along with.