Iran incurred some losses, no doubt, however the myth that Iran has zero air defense systems is a talking point spread by the West to bolster their supposed victory.

A portion of Iran's Air defense systems were destroyed, however a significant amount were simply disabled via cyber attack for a period of about 8 hours at the start of Israel's attack, however these have been restored.

Also, Russia has air defense systems that also protects portions of Iran's airspace so it's not exactly defenseless in that regard.