At that time the brits, the colonists had plenty of time to reform, just that no one were ever interested enough in that poor uninhabitable land to pour enough resource to it, even if history repeats itself, no one would. Hell, we hardly do enough in Africa today.

Well this is becoming a very complex argument. We can speculate about the political and economical conditions for reforms, which may not have been present in the UK (not set on that, but possible).

But when we look across history and search for desirable models, neither the UK (or any other) colonialism nor modern annexations by totalitarian regimes seem like the best outcome (from an enlightenment/liberal POV).

This is not so complex, it's someone else's backyard. Unless the US or the EU is seriously considering the possibility of pouring money into the conservation of minority languages on the native people of their own land. I'm not convinced.

The idea all culture exist and will all continue to exist as-is is a beautiful, beautiful dream, and also an expensive one. Gentrification is San Francisco is the obviously example of how fragile local cultural groups are in the face of industrial producticity.