well they are and they aren't. it's hard to just ignore 70 years of visual iconography.
assume a mexican dude were cast as superman in the next movie and a chinese dude were cast as batman. i could be wrong but i just don't think the fandom at large would be universally behind it. no matter how hard they try and cape for ethnic diversity.
You can ignore it when the visual iconography is the way it is because they weren't allowed any other way breh. This isn't a thing where these characters are white because they just had to be white or they're defined by it; they're white because they weren't allowed to be any other race because any other race was thought to be less intelligent and less advanced and just less than a white man or white woman. And if you want to say you can't ignore visual iconography,since when has batman been shorter than his love interest? Since when has batman had a receding hairline? Since when has lex been a small cat like Jesse Eisenberg is in this movie? Or to your earlier point, since when has batman been bigger and taller than superman? You can ignore certain things but you can't decide to make lex black the same way they decided to make perry black?
Again I got no beef with it at all but I don't buy your logic because changes are made and characters are played with and interpreted in different ways on the regular now. I remember the mini outrage when they made perry black all while people seemingly forgot they cast one of the best actors around to play him in Laurence Fishburne