Honestly, I go back and forth a lot on these "controversies." I do think for a great many of the most incensed it really is a(n unrealized) matter of taking issue with not being pandered to. These folks typically don't think of pandering as something that can be done toward themselves in the first place (which is a whole other topic in itself).
At its most basic, though, these complaints about accuracy are taking a fundamentally okay point too far, I think. There probably are times that race needs to be preserved -- T'Challa/the Black Panther or Luke Cage are good examples for what I hope are obvious reasons. Even looking at White characters, though, maybe Steve Rogers. That the ultimate soldier sent to take on Hitler's war machine was a blond, blue-eyed man has value.
Now, could there be value in having Steve be Jewish or Black (or homosexual or disabled for that matter)? Yeah, probably. I'd even say there's probably more value in going one of those angles than keeping everything about him the same but making his hair red or dark brown. For myself, though, when I think of what's iconic about him on and what resonates thematically, you've got to pull from the whole "perfect Aryan man" thing.
When it comes to MJ, what I think of as iconic with her isn't her race or skin color; it's her hair color. And yeah, it would be stupid of them not to keep that accurate, but keeping her race comic accurate isn't even necessary to maintain the plausibility of a Black MJ having red hair since there are Black people with red hair. Especially if they're of mixed ancestry like Zendaya -- whose White half is of Irish descent, for that matter.
Long story short, there are considerations worth making (don't cast MJ as, I don't know, a 57-year-old Mexican dude), but there are way too many hills that aren't worth dying on. This is one of those.