Iranian missiles don’t seem very impressive, tbh. They don’t seem to pack much of a punch, and they get intercepted way too easily.
In contrast, Russia’s Iskander seems to get through Ukrainian AD with little effort; American Patriots usually struggling to stop them, often requiring 5-15 Patriot interceptor missiles to take out just one Iskander, at least from what I’ve observed.
Plus they seem pretty powerful, pack quite a punch, and come with a variety of effective warheads, particularly the HE Frag. airburst variant, which turns everything into Swiss cheese and makes the HIMARS tungsten ball-filled warhead pale in comparison.
Propellent mixture, grain geometries, exotic materials, nav and terminal guidance that doesn't sacrifice speed for accuracy and allows some margin for maneuverability. It's hard.
You need to build the shit out of the entire vertical industry. Academia to motors to test ranges.
They have the capacity to build something like 50 missiles a month but they aren't able to move to higher end ones nor do they have the ISR to use them as effectively as more advanced militaries.