And also, hasn’t Iran proved that they can knock down the f-35s?

They hit one, out of how many that have been openly flying over Iran, day in and day out.

Probably, it managed to fly low over the one tiny patch of land that had a shoulder launched missile operator on it, and did so in broad daylight. That day, remove any of those variables, and the survivability goes from 99.9% to 100%, without even being careful.