the last time US wanted some country to reset back to Stone Age the same thing happened. turn out those aircrafts are not undefeatable at all.
The only ones I'm seeing act like there should be no expectation of losing aircraft in a war are social media figures who always want to bloviate about something.
It's pretty normal for planes to go down in a war. They've flown 5000+ sorties, it's a pretty huge accomplishment this is the first one lost over Iran. Especially considering all of the last decade's speculation about how tough attacking Iran would be.
You'll never be able to fully suppress all of their manpads. Even if you destroy the bulk of their air defence network.