Yes, because a traditionally white role being cast with an actor who's race is often underrepresented isn't affecting the whole swath of white-led films and shows. Casting a lead role which is traditionally associated with a minority as a white actor takes away one of the less common instances of a minority race being represented as a lead in a film.
The situations are not equal, so you can't draw equivalencies between them. If Hispanic women were cast as often as White women in films, you'd have a point. But that isn't the case.
Another issue is that minority characters often have their race be a part of who their character is. Black Panther has to be black because his identity as a black African is tied directly to who is character is and what he represents. Whereas Peter Parker can be any race because he's just a nerdy kid who gets superpowers. His race isn't important to who he is as a character and what he represents.
We often see these with white characters. They have defining characteristics other than their skin color. They are just "normal" people. If Superman is Black or Indian looking, it doesn't affect his story of being an alien from another world trying to blend in and save humanity.
As for Snow White, she should be the fairest in the land. Now, if this land isn't a European-based land, fair might be a different complexion to what we consider fair. If Snow White was set in the heart of Africa and Zendaya played Snow, it would make sense. She's fair skinned for a Black woman. They might say that her skin is as white as snow.
All in all, I don't care what they do with Snow White. As a character, she is pretty dull. She's pretty and nice, those are her defining characteristics. She doesn't have any agency in the story. She flees when she's told to flee, she hides out with 7 men, and then she eats an apple from a stranger. If they make her interesting and compelling, then her complexion is a non-issue for me.