I think we can probably pretty fairly criticise a lot of Marvel and DCs characters for being antiquated and racist as a product of their time.
The controversy over Iron Fist seems less about that, to me, and more that Marvel had an opportunity to cast an Asian actor in a lead, and chose not, which is particularly damming because there are no Asian actors currently playing Superhero leads.
That's fine - I support that. I'd like to see an Asian lead in the name of diversity. I don't particularly like how this has become so conflated to make Iron Fist, in particular, some kind of racist white saviour trope. That's just not his story - I see that complaint quite fairly levelled at stuff like John Carter, Tarzan and to a lesser extent The Phantom - and it's true that those characters clearly bore some influence on Iron Fist. But this criticism seems to really easily forget how much of a celebration of multiculturalism Iron Fist became - I mean Second Genesis was 1986 right? Long held as a great turning point in diversity for the X-men. PowerMan and Iron Fist was 1972 - and I freely admit there were some tropes there in the early days, but by 1976 you had Misty Knight, Colleen Wing, Luke Cage and Danny Rand working together to take down a lot of villains which were mostly oppressive jerks or corporate dickheads who were the natural enemies of Heroes for Hire.
I just find it sad. Trump Sad. It's like saying "Wolverine should be Japanese because he knows samurai stuff - therefore, racist" and not looking at any of the good the character got to be a part of.