It's a study in human foible. What responsibilities do we have to the people we live with, whether they are family or strangers?
Their hubris was amazing. But are supposedly nice people really all that different now? The ability to misuse another person and then find reasons to excuse it is a universal human trait.
We hope they will realize that human nature contains both compassion and cruelty and that we all are capable of both. In either case, you are responsible. Nobody gets off free.
You want to be like them -- at least in the first part of the play.
The British Empire was at its peak. How could there be anything wrong with a society that was so brilliantly successful?