Your historical understanding is clearly very limited and deeply biased. As a starter - NZ was never a colony, even if the British over some time clearly behaved like colonisers ... and yes - do some reading about the history of European colonialism - it is a dark chapter in our history full of dead and exploited people and blood spilled all over the floor.
Did humanity benefit from industrialisation and modern medicine? It depends whom you ask, but for the majority of people alive today (no matter whether they are white or brown) clearly yes. Has though nothing to do with colonisation which throughout history always used to be the subjugation and exploitation of the weaker group through the stronger group of people ... Law of the jungle.
Did Maoris benefit from being cheated and killed? Well, the ones which were cheated, suppressed and killed by the Brits probably not.
Do the surviving Maoris live today a better life than they would have had without any contact to the Europeans? Hard to measure. How do you define a good life? Life Expectancy? Freedom to choose? Self determination? The right to use their property as they see fit? The right to use the property we stole and cheated from their ancestors as they see fit? Pride? Education? Respect in the society? Happy family life?
I suppose measured in some of these categories (and there will be many more) do they live these days a better life and in some a worse. Maybe we should ask them how they feel? Obviously - we can't ask the ones who died.
How do I see race relations in 100 years? Not sure this is a NZ specific question, but world wide is the reproduction rate of people of European descent below the rate to keep the population constant while the reproduction rate of many brown and black populations is well above this rate. You don't need to be a rocket scientist to extrapolate what this means for the future.
100 years are four generations or so, and at that stage the power balance as a consequence of this process will look quite different - in NZ as well as in the world. I do hope that the Europeans still manage to set up a fair system for races to live peacefully and respectfully with each other ... otherwise the stronger and more populous populations will do this for us, probably based on the experiences they had with us, the ex-colonisers.
I hope that we will be able to create a fair system, but if I listen to all the white superiorists and racists, than I do have my doubts it will work out well for us. I just hope that the people with darker skin don't treat our descendants in the same way we used to treat their parents.
Better would be if I could wish for the people with darker skin treating our children at that stage the same way as we treated them ... but I think in this case the Europeans need to change some things - and fast.