Hypertime!
Is DC the only place in all of literature, movies, and comics in which many of the heroes are omnipotent except for one silly weakness, and the villains have to work harder and try to exploit that weakness? I mean, there’s Superman and kryptonite, MM and fire, there’s even one hero who has a genie or something that can literally do anything. The villains? Lex Luthor, a human. The Joker, a crazy human. And yet these human villains get enormous power through skill and cunning, while the heroes are already blessed with omnipotence and can’t stop them once and for all.
Its a fair complaint. Marvel’s heroes have incredible powers, but at least the villains tend to match them.
DC in contrast have the over-used Darkseid, and few others. (Although I see Krona is making a return for JLA/Avengers.)
The Martian Manhunter went under a huge retcon. Not sure if it was due to the crisis or just because.
He was gone from the JLA for so long because supposidly his people were still alive and he went to join them on a new planet dubbed Mars II.
He appeared occasionally during that time period, but not often.
He returned to Earth with a warning of Martians wanting to take over the Earth. That series was what brought the original JLA to a close and started the Detroit run.
Later it was said he never left Earth and that his people had been dead for millenia.