Lots of people seem to be jumping into this thread automatically shouting 'you're SO racist!' without actually reading and responding to the discussion in an intelligent way.
I don't see people here saying Ambika Mod is a terrible actress/ ugly/ doesn't deserve to play a leading female role? She's obviously a lovely person, talented actress with a great future ahead of her.
What people are trying to debate is the impact of casting a (any?) brown-skinned actress in THIS adaptation of THIS book, which, while undoubtedly fiction, is not fantasy.
Plenty of people have commented that from their experience of 1980s university life in similar universities to Edinburgh, this casting decision massively undermines the authenticity of the story for them.
Historical accuracy matters to a lot of people (me included) and a lack of due care and attention to it can ruin any production. It mostly matters to film and TV production companies too, which is why they hire expensive historical researchers to make sure props, costumes, locations are all as authentic as possible.
Why is it important? Because it 'grounds' the story in a particular era, with people using the cues to make sense of it. Imagine if the producers had said let's set it in the 1980s but give everyone smart phones - we'd all be here saying how stupid and unbelievable it was.
That's all that people are saying here - that for them the casting choice of Emma is jarring and unrealistic. It spoils their enjoyment because based on what they know of the history they are constantly thinking 'no, THAT just wouldn't have happened like that...'
It's not about being racist, or critical of Ambika. If anything, it's being critical of Netflix and the production company.
A lot of people disliked Bridgerton for the same reason.
If it doesn't bother you, then great, go ahead and enjoy. However that doesn't mean that either point of view is right or wrong - they are equally valid opinions on the adaptation.
FWIW, an Indian friend of mine is also critical of the casting of Emma, and argues that it whitewashes the awful experiences many Indian/Pakastani students had at university in the 80s. It is also hugely 'jarring' for her too! Make of that what you will.