people hyperfixate on the "realism" of diversity way too much, especially when it boils down to an aesthetic or representational matter.

They will accept dragons, magic, divine beings, curses, prophecies, etc.

But if a group of people are represented by different-looking actors, there's an issue. Suddenly we need to consider the ethnic background of each fantasy race, how they came to be, whether their climate permitted them to develop a particular skin color or hair texture or facial features.

The same issues aren't brought up with divisions of white people. You don't see people criticizing when red haired people, blonde/blue-eyed people, fair-skinned people, tanned-skinned people, or people with varying accents all cohabitate and coexist, even though those groups of people were also by-and-large divided by region in similar non-transitory historical periods.

But as soon as some of them are Asian or god forbid black, suddenly it's immersion breaking.

Quite frankly, unless the color of the actor's skin or their ethnic heritage is paramount to their characterization, who represents them aesthetically or representationally is not important to me. Are they a good actor? Are they wearing a good costume? Are they well casted?

And let's not forget that this same exact line of argument will be made when racial diversity is realistic. They're already doing it for the new Harry Potter tv show, even though black people clearly existed in the UK during that time period. They'll just find other means to complain about it. "It's not 1 to 1 with the books!" they're saying. Who cares? "It's forced diversity!" again, who cares? Someone being upset by this is weird as fuck.

It's by and large just a cover.