Nope, half the population doesn't die in Final Crisis.
> Renee Montoya is the savior of the world,
We haven't seen Montoya since FC, Jeez!
> and the Monitors live among us
I believe that you are confusing the lack of inmediate referencing with retconning out. And cinse the monitors live among us AS HUMANS WHO LONGER REMEMBER THEY WERE MONITORS please notice it is a bit hard for that to be referenced so casually. Maybe it will be part of an upcoming story, or not. But it hasn't been retconned out unless you have a extremely draconian rule that says anything that hasn't been mentioned in a month is out.
> plus Aquaman is floating around for some reason whynot
I fail to see the retconning there.
> and the Hawks are maybe dead except they aren't.
Here is the thing. Dc editorial was not sure if they wanted the Hawks dead or alive. Morrison got tired of waiting for a final decision on that and on purpose made that scene confusing so they could finish deciding later. Good thing because in the end DC decided they wanted the Hawks alive... weeks after Final Crisis 7. That's why McDufie complained because he worked with the idea that they were dead while writing JLA #31 and had to change a scene in the last moment to something that doesn't make much sense.
So no, it wasn't retconned out because Morrison stuff has to be erased, it was retconned because DC changed their mind.