I wouldn't ever ask the internet to turn you off of a movie you already like, but anyway IM3 is excellent, one of the best so far in the MCU (and my favorite). People that have the biggest problem with it are disappointed that the Mandarin wasn't what they wanted, even though it would have been a tired retread of an ethnic movie villain had it been played straight. The extremis enemy was a refreshing change, as the first two movies were "fight another guy in another Iron - something suit."
It explored more complex character traits like ptsd and anxiety, and was funny, witty, and interesting. Iron Man is not the suit, it is Tony Stark, that is the entire point of the film. People upset that there wasn't enough "Iron Man action" are missing that point.
People upset that the Mk42 isn't invincible are also missing the point, it is supposed to be an incomplete prototype of a stressed, broken man who is overwhelmed with the risks he sees in the world- as was the entire HPP, a crazy ensemble of specialized suits, most of which weren't built to fight in the first place.
He got the surgery after he realized he had conquered his demons and could finally live without the arc as a crutch. He was scared to have the shrapnel removed, would doing so also remove the only thing that made him a hero in the first place? He can finally believe in himself again after he saves the day with only his wits even while losing his mansion and all his armors, that
he is Iron Man, not the suit, not the arc. "Best sleep I have had in years."
Plus a crazy action scene with 35 Iron Men, that's the definition of having your cake and eating it too. You get to hung up on the preconceived notions on details you have built for yourself, you are going to hate everything (see: 90% of the discourse on the internet). Learn to appreciate
Shane Black while you're at it, he knows what he's doing.