What exact commentary is Iron Man 3 making on racism and xenophobia in general? It really isn't saying anything about those topics at all. A plot point is not a theme or an exploration of an issue, it's not collecting Pokemon cards and saying "see we got this too". A story has to commit to exploring a theme and it being integral to other aspects of the story for there to be any value there, it's not a "check box" of features like a video game having different features.
If you believe that A New Hope's comment on mysticism over technology because of a five second scene at the end is "commiting to a theme", yet the central white American millionaire villain's entire plot being the use of the quintessential generic Middle East looking terrorist knowing it would be bought immediately by Americans is not a comment on xenophobia, this conversation may have run its course, sorry.
While I would agree in that regard, I would also argue that specifically A New Hope is a different animal from the MCU in their blockbuster roots. A New Hope is an underdog success story conquering cinema, a weird celebration of pulp sci-fi rooted in everything from Kurosawa and classic Arthurian legend to WW2 adventure, that somehow came together in a cohesive manner, while also being a groundbreaking visual effect milestone at the same time. Not to mention the examples of efficient visual storytelling like the opening scene.
A New Hope exists in the same pantheon as Jaws in establishing modern blockbuster cinema. Iron Man and the rest of the MCU don't have that kind of foundation. They're just blockbusters, beholden to what A New Hope cemented with its success, in simply being as well-received as it was and in showing how high-concept sci-fi and genre film can resonate with general audiences. A notion that the MCU benefits from today
I do not dispute any of the above merits in regard to A New Hope. We were arguing specifically about movies having to be enlightening to be cinema, which A New Hope, dear to my heart as it is, is not.
At the same time, downplaying the success of the MCU to revitalize the superhero movie genre, financially if nothing else, is being the same kind of nostalgia biased that makes people feel justified in making a profound categorical difference between them and A New Hope.