Netflix released the original show “Supacell” with new and original characters, but in the comments, right-wingers are complaining that the protagonists are black. The film quiet place day one was released and had a black protagonist. The character is new, original and coherent. Quiet Place is set in the USA black people exist in the USA, so what’s the problem? If they are going to complain anyway, then why do they ask to make new characters?
There are two distinctly different topics in your question. The first, yeah, there’s some legitimate arguments to be made that core identify traits of beloved characters shouldn’t be changed. Notice I said “arguments” because that statement will certainly start one from people on the far ends of both spectrums. The second is people complaining about original characters being black. That’s probably just racism. Plain and simple. No need to dig deeper.