The cultural aspect is the most interesting to me.
To the degree the natives & the invaders meld cultures things smooth over and a couple hundred years later all that’s left is some small fraction of ethnic natives who celebrate the Good Old Days and nurse their (justified) grudge.
To the degree the natives want to, or are forced to, live separately in enclaves as if the invasion never happened, well that’s simply a recipe for a frozen conflict and eternal resentment.
Ultimately, most human cultures progress over time socio-politically, technologically, and economically, albeit not all at the same rate or in the same exact directions.
A native population that chooses to say “Our culture in year X just before the invaders arrived defines us forever. We must hew to that standard with no progress forevermore” is choosing to step off the escalator of history and enter a vortex of permanent failure and despair.
IANA expert on the details, but when the Spaniards encountered the Maya, Inca, and Aztec cultures the sociopolitical differences were small (kings & priests in charge, a merchant class, and a mass of peasants), the technological ones represented just a few hundred years progress, and the economics weren’t that different. A pocket of mostly still purebred Incas choosing to live the old way now in the 21st Century have chosen to be left vastly behind.
The error in a cultural absorption is the natural tendency for the absorbed to fetishize their immediate pre-invasion culture without recognizing that it quit independently evolving at that time. Had the invasion never happened, it would still have continued evolving from that time forward to today and on into the future.
IOW, just as white NZ culture has changed since the 1800s, so would have undiscovered Maori culture.
To be sure, history is full of examples of cultures that got stuck; thinking “we’re as advanced as we want to be. Change is Evil.” And almost all of those have been eaten by more advanced cultures in classic Darwinian fashion. Russia’s current klepto-fascist political culture and gangster-centric economic culture is busy being destroyed from within even now. It may not go quietly, but it’ll be unrecognizable in 100 years.
Progress is not guaranteed. The world may become more of a dystopia than a utopia. Change however is guaranteed; entities that want to live in the Goode Olde Dayes according to the Goode Olde Wayes are doomed to marginalization and decay.