Air defence is a skill issue
that's what I was getting at. The Iranians should be getting at least some kills and missile knock downs, but they're just not... or maybe they are and the US just isn't reporting on it because they must maintain the perception of US air dominance. although even if the latter was the case, it's clearly not enough cause Iran is getting pummeled right now.
and also about Suppresion of Enemy Air Defence (SEAD)
that's the purpose of an IADS, to defeat SEAD. The major problem with AD is tracking and targeting radars have to be designed and tuned for specific targets. Planes, missiles, and drones all have differnet radar signatures and fly at different speeds and altitudes, so you need radars specially designed to target and track each target type. So if you have a single AD system with a radar designed to target and track planes then sure it can do that, but the moment it starts to emit and launch misiles, it's going to have an anti-radiation missile or maybe a drone coming for it.
Well with an IADS, you don't have just that one AD system. It has multiple other AD systems supporting it in an area, and each of them is supposed to be able to engage different targets. So you have your long-range SAMs to engage incoming planes and ballistic missiles, your medium-range SAMs to engage incoming cruise missiles and larger drones, and your short-range and point defense systems to engage small drones and ground-hugging cruise missiles and anti-radiation missiles. In theory, this creates a bubble that is supposed to be impentrable by the enemy's air assets. But clearly, either Iran is not implementing this IADS theory, or their equipment sucks, or as you suggested their troops are just too scared to turn the stuff on and get blown up (only to get blown up anyways).
As for jamming, that's why modern AD systems now employ multiple targeting systems and seeker types. They'll launch on just a bearing track from the ground radar, and then once the missile is up in the air it acquires a better target track using it's own suite of seekers. And Iran has received advanced systems like this from Russia and China. they're just not using them properly, which again comes down to the poor quality of their personnel.
F-117 is a complete non-sequitur
I know, I said L/O tech has advanced beyond since then, I was just using it as an example. Also shapes do still play a part, the hull shape of the F-22 and F-35 were both designed following L/O principles. You can have all the RAM and jamming you want, but if you're flying in a badly-shaped bird it's going to light up like a chrismtas tree on the enemy's radar.