yitay, the rambam doesn’t just say that “one need not (or should not) accept all divrei aggada as historically accurate”. He actually goes into great length in describing the people that do as idiots.
He says there are 3 types of people:
1) those who take aggada literally – people who are so full of themselves that they think they understand the mashalim given by the rabbanim; that it is beyond possible for the rabbis to perhaps have had a deeper meaning.
2) those who won’t accept anything bc it seems impossible
3) and those who accept that aggadata was designed to have a deeper meaning and no one is expected to take it literally.
as rabbi yitzchak berkovitz of the jerusalem kollerl says, who cares if the story in the gemara is true or not- maybe they lied! The point isnt the truthfulness, it is the lesson to be learnt from it.