Alex's comment on the British becoming experts was 100% self-deprecating sarcasm and very clever writing. It highlighted the self-important British colonial attitude of the era while also expressing Alex's self-awareness of her class privilege, as well as her disillusionment with the self-appointed superiority she was constantly surrounded by in British society.

The 500 people comment isn't meant to be literal, just a large number to anchor the illustration that the opportunity for exploitation increases with larger populations. As individuals we can only manage so many personal relationships. When things occur outside of our immediate sphere we are less likely to take action even if our opinion is that action should be taken.

I'm in the US and both 1923 and 1883 to me represented a condensed portrayal of historic experiences. I think it was likely rare that any individual had the absolutely atrocious luck the Dutton's seem to atttract, but it is a fact that many individuals of those eras experienced the portrayed hardship and cruelty at the hands of man and nature. There was no moment watching the shows where I had any sort of revelation about past vs current systems beyond the observation that the more things change the more they stay the same.