Representation in fiction is a controversial subject. Women are famously underrepresented in fiction, with various tests designed to reveal the status of female representation in individual movies and the industry as a whole.
Studies show that men feel female representation is equitable when 1 in 4 characters are women. When all you know is privilege, equality feels like oppression.
Then we have blowouts over castings of previously white male characters with actors that are not white male.
This happened with Knuckles the Echidna - who was intentionally inspired by Jamaican culture - when a fan artist depicted him as black. It happened with "black female 007", which was ridiculous considering James Bond was still a white man. If my memory serves, James Bond was fired by MI6 as 007 and replaced with a black female agent, who then ends up being mentored by James Bond anyway.
It also happened with a Harry Potter stage play where a woman of colour was cast as Hermione, whose skin colour was mentioned once in the seven books.
Most recently, it happened with Leah Sava Jeffries - a black girl - being cast as Annabeth Chase in the Percy Jackson TV Series.
The most common arguments are "we shouldn't change existing stories" and "just make new stories with proper representation". As someone who's read loads of fanfiction, I can barely understand why. A story whose plot, setting, or characters are based on another with varying degrees of fidelity is not new to me. There is no rule saying the inspired work must not be made by the creators of the original work.
In addition, the race and genders of characters are rarely, if ever, relevant to the plot, so how does it matter?
In my opinion, plain and simple racism and sexism.
Related: when a characters race is not specified, what is the default race to cast them as? And why is there a default race?
My first exposure to the idea of homosexuality was it being used as an insult. For a while I believed gay people did not exist, and it was just a way to call a man feminine.
Rick Riordan's representation with Nico di Angelo and Alex Fierro was the trigger for me to learn about LGBT+ lives. Representation matters.
The early books in the Percy Jackson series had common hair and eye colours for demigods of each of the Greek Gods. While this was core to my engagement with the universe, it really didn't hold up in later books. With confirmation coming that the TV Series will not have book-accurate hair and eye colours, I still need some time to grieve the loss of that aspect of worldbuilding.
What makes it easy is the fact that I don't want to be associated with racists, who used the same excuse to pile on Annabeth exclusively. Rick Riordan's take on this is that this series is just one of many valid interpretation of the books. The world in my head where hair and eye colours matter is just as valid as the series where they don't matter.
More evidence that outrage over "changing the characters" is rooted in bigotry is that whitewashing is barely protested. Jesus isn't white, the Ancient One from Marvel isn't white, and neither is Steve from Minecraft.
This last one is most revealing, in my opinion. Steve is quite obviously Brown in canon. Minecraft has shot up in popularity lately, and many people see themselves in Steve. Since Steve is so relatable, what is the race people expect him to be cast as in the Minecraft Movie?
I can confidently bet that had they cast an actor of colour as Steve, there would have been backlash.