I hate that being against race-swapping (major) characters means being racist now

Boo hoo, Severus Snape was never meant to be a black man. I read and adored Harry Potter as a child, and watched all the movies multiple times, and Severus Snape was never, in my mind, a black man, and I'm saying this as a person of colour. Same deal with Annabeth in the Percy Jackson show - She was explicitly blonde with grey eyes, and thats how I imagined her all throughout the books, but I've seen several people accused of being a racist just because they were against the casting choices. Same with the new Captain America movie, Anthony Mackie simply does not have the charisma to be a leading man, especially when the previous herald of the mantle played the role to perfection. I can understand the minor characters, hell, I absolutely did not mind the Velaryons from House of The Dragon being black, nor the new Doctor Who and loved their casting. But newer movies, instead of creating new badass characters of colour, often resort to baseless race swapping.

EDIT : Yeah, upon second thought, Anthony Mackie as Captain America was a bad example. It's just that I watched the movie and the show very recently, and did not really like his performance. Most of the comments criticizing him were downvoted into oblivion in the discussion thread, and accusations of racism were flying rampant.

EDIT 2 : I'm getting a couple of accusations of racism, and I think some points are valid. I assure you, the three examples are entirely based on what I watched/read,and not the specific race. I would like to ask, how would you all feel if Miles Morales was recast as a white dude? Because his race is not really essential to his story, but I still would hate if he's a white guy in the latest spiderman.

EDIT 3 : Half the comments still call me racist for caring about a fictional characters' race. Snape being black would introduce a lot of negative racial connotations. The other half tell me Miles' Morales race is essential to his story, but absolutely none of them elaborate how his story would be different, had he been, say Asian/Arabic.