Would bringing back Iron Man be worth potentially degrading the quality of the MCU overall?
It would be exhausting to never trust that any hero is gone forever, and frequent re-introductions would run the risk of the MCU becoming too complicated and convoluted for the mainstream audiences to care.
Like it or not, the mainstream is what keeps the superhero genre a blockbuster affair, so driving them away would almost surely mean the death of those days.
Not to mention if you bring back one of the MCU’s biggest characters, you open up the can of worms where it’s hard to justify any hero will stay dead or gone forever.