The views of individuals don't necessarily matter; it is plausible that individual leaders or soldiers still were as ruthless as ever, but if the population no longer supported it, it would be a political dead-end.

But yeah, "stuff I read in fan fiction" is on the lowest tier of my information-trust-chart. I'm a bit curious about why the British did give up on colonies. Was there really a sea change in British public opinion over the course of the World Wars? Was it a moral decision or an economic one? I could think of a dozen of reasons, which makes none of them worth speculating about aloud, but honestly this part of history is also pretty low on my reading list...