Correction: Jean's resurrection forX-Factor was one of the worst things to happen in X-men. She was fine from her appearance to death, but that was her character arc. There is nothing more you can do with her as a hero, because she has a character arc where she destroyed an entire civilization. Retconning that away won't help because then you take away a neat character arc where she needs to face that. And even so, it all goes back to Phoenix power level crap. Jean really only seems interesting if treated as a morally ambiguous character, but they always want to treat her as this benevolent woman.A clear case of cognitive dissonance from Marvel, and many casualfags who like Jean because she is one of only 3 X-women normies know, so it automatically makes her great.
And it's precisely for this reason Rachel was the best person to replace Jean on the contemporary X-men. Execution aside, she comes from a morally bankrupt upbringing and setting, thus there's already a built in conflict of her wrestling with what she's done and wondering if she's even right for the responsibility of continuing her mother's legacy, kind of like a Barry to Wally situation. She could be the opposite of her mom, coming from a dark background of death and violence, but rising up as one the strongest and most heroic X-men. She would've been a much better long term member than Jean post Dark Phoenix.