MANPADS have a range of around 4 miles. Most soldiers aren't carrying around armed MANPADS. They have to fetch the MANPADS, arm it, aim, and fire all before the jet dumps its load and flares before bailing out. Because of this, MANPADS are a much greater threat to helicopters or CAS like the Warthog than they are to jets dumping ordinance. This has been proven pretty decisively in Ukraine.
Radar is line-of-sight. A non-stealth fighter flying just above the treetops can only be detected if it gets within a few miles of a SAM radar. This is true to the point that the radar lock range for something like an F-35 is about the same as a non-stealth jet flying super-low (though the hit probability is lower for the F-35 if it's flying at high altitude as it has more room to detect the launch and maneuver).
The problem is that CENTCOM is actively lying to us. After this shootdown, they denied it happened while launching search and rescue operations only admitting to the facts after Iran released the evidence. The same thing happened with the F-35. CENTCOM said it landed safely, but were simultaneously sending an Chinook to run search patterns in the area. This could also mean that the alleged Kuwaiti pilot that supposedly took out 3 of our F-15 was also a lie.
Finally, with so many non-stealth planes getting shot down and stealth allegedly working great, why are we using so many stand-off munitions still and why aren't we using F-35 more?
All the shootdowns have been shown with a custom software showing an IR view and the successful missiles seem to be using electro-optical tracking. The IRST is passive and doesn't trigger sensors plus isn't stopped by our radar stealth. At the same time, a human operator means stuff like flares don't work anywhere near as well. Even more scary, these human-guided runs are premium training material for China to train AI-guided missiles.
My conclusion is that stealth is no longer the game-changer it was once though to be (if it ever was).
Drones and munitions depth seems to be the name of the game, logistics wins wars
After the bombardment by Israel last year Russia sent a ton of Manpads, so they are certainly available. We've seen a very close call by an fa18 from a manpads. It's likely that Iran has passive sensor networks that they can use to spot patterns and provide forewarning to manpads teams.
I think you're right about stealth not being quite the game changer that it was. The Houthis were able to give f35s some close calls over Yemen last year. They're of course armed and trained by Iran, so we would expect to see some hits.