It was born old and decrepit.

The Illuminati could have appeared in either Avengers: The Kang Dynasty or Avengers: Secret Wars

I mean it was cool but they just killed off everyone instead of giving them a proper role

They didn't age at all after that

Not sure what you mean by “aged well”. If anything it is the start of what might be a trend for Marvel in having no regard for characters from other universes, no matter the actor or character they are playing. I expect much of the same in the next two Avengers films and maybe with Fantastic Four (since they seem to be coming from a different universe too).

I'm sorry but these guys would always stand zero chance against Freaking the Scarlet Witch. Girl almost beat a 99% powered Infinity Stone Thanos by herself while destroying one of the Infinity Stone at the same time. She can handle a few heroes.

Also, we kinda don't need them for Doomsday and Secret Wars.

JMATIUAS, I don't remember if it was revealed that Avengers: The Kang Dynasty had changed its title when you posted that, but the title of Avengers 5 is now Avengers: Doomsday.

@Paperinick It did, he just refuses to call it Doomsday.