But that is exactly how you fix the problem, There is no subtext to be had here they are too many white characters for other characters to get shine the need to be less. If you outright, replace white characters with new characters people will complain, So they try the middle solution of making some of these characters a minority keeping the character around in a form. We aren't talking about real people we are talking about fictional characters and the fictional world, If you remove Wally West he isn't dying, In fact if you remove Wally West, They are still 4 or 5 white Flash characters running around. You remove Tim Drake, They are still 3 or 4 white robin characters running around. And if you are looking at erasure then white characters for years have been erasing minority characters and why is that okay?
I will address the other thing many white American characters race has zero impact to the character, While dam near every black character race and culture are things that are brought up in their stories. It took years( I mean decades) for Bruce Wanye and Captain America to be Irish. It is easy to talk about replacing race when it is not part of their story in a meaningful fashion. They are very few minority characters like say Blade whose most of their history and stories race doesn't play a strong part.
Hawkeye, Bruce Banner, Hank Pym, Oliver Queen, Hal Jordan, Barry Allen what is their background in terms of culture? These characters have been around for decades and culturally you can't tell anything about these characters. If was Iceman, Magneto, Kitty, Ben Grimm, Captain America it is a different story. Sorry a lot of white characters are blank slate when it comes to things about culture and race barely plays a component in their story. Nobody is saying "the white race" doesn't matter but it is true that many white characters were created and existed without any care for things culturally. That isn't the same for most minority characters and I can find stories in most case where race is a factor.