What kind of new, clothing, and architecture would you use for the rulers of the elemental plane of fire if you got to redo it?
I mean, to start move away from the whole "They're all genies". I think the Djinn are good enough and we can move Efreets and Marids to unaligned malevolent spirits, which probably in-keeps better with their origin and is, arguably, a more interesting place than "A different kind of genie". They can still have some sort of relation with Djinn (Are Efreets and Marids exiles? Lost tribes? Distant cousins?), but let it be less set in stone as to how it is.
Make Djinn broader overall and have there be no set alignment for them; without the whole elemental theme, you don't need them and suddenly you can intrigue and strife in the Citadel of Ice and Steel. You can have evil Djinn, Djinn that form from sand, smoke, wind, etc... having diversity inside of a creature set instead of creating whole new ones to occupy different spaces. Now there are reasons to go to this fantastic falling orb in an endless sky, and it doesn't have to share time with the City of Brass.
For the Plane of Fire, move away from the City of Brass. I think going to something closer to the original tale is actually a better idea, so I would create smaller city-states on the Plane of Fire and go with my Elemental Hansa idea. For the other planes, I'd have to think about it: I'd love to see different kinds of elemental creatures with interesting cultures, given that Marids obviously didn't get as much focus and Daos are straight-up brand new.
I am not so sure that stereotype has much currency these days. The only time I hear about it is in debates about US slavery (ie what about African or Arab slave traders?) or in serious political discussions about modern slavery (and then it isn’t typically applied to Arabs as a group). And awareness of modern slavery is quite recent. My sense is most Americans know very little about that or about historical slave traders (beyond what happened within the US): they are much more likely to lean on stereotypes of fanaticism, attitudes towards women, and terrorism than slave traders. But in D&D one of the features the alignment system used to always mention with Evil, was slave owning societies were evil. So I think it is more s stand in for them being evil than for them being Arab coded.
I mean, I don't know what to tell you other than these tropes absolutely get overused in trying to depict Arab culture badly. Again, you can have an evil nation that happens to be Arab, but when it plays into the most obvious stereotypes of Arabs, it should be called out.
And I can't speak to your debates, but I've absolutely seen it all over being used as a bludgeon to attack Arab culture as well as to distract from the horrors of our own slave past. It's not hard to find these online and when you create races that are obviously coded Arab and play into these tropes, it's just bad. I mean, we can talk about the Efreet, but it's worth noting that all genies have slaves in 5E, even the canonically
good-aligned ones. So it's not just a "these guys are evil" thing.