I think you should read a book on the history of the British empire. The point you're responding to is basically correct. The idea of the "noble savage" as it was once called is a fantasy. The countries invaded and conquered by the British were typically brutal empires with medieval or lower levels of development, and had been that way for thousands of years with apparently little or no cultural development. The British were encountering local rulers with spears and they had Gatling guns. These societies had no technology, no science, no education or healthcare, primitive to non existent infrastructure of state and oh, they were mostly slave-oriented societies.
Yes the empire was a dictatorship that conquered them and in the early era, bought slaves from the local rulers. In the late eras the empire built infrastructure, education systems, brought modern medicine, tried to teach civilised values like not beheading your political opponents and having votes instead, and in some cases as the empire faded, left the countries in a vastly better state than they were found.
Colonialism is easily one of the most complex and ethically grey areas I've found when studying history. There is no evidence or reason to believe those societies would have ever advanced were they not conquered.