It's worth noting that Chris Terrio (the writer of acclaimed films such as Batman V. Superman: Dawn of Justice) was also a writer on this one - not just JJ.
I'm not sure who did what or how that balanced worked, but I place a lot of blame on Terrio's involvement (maybe unfairly so).
Rose and Maz were needed on the base to give Carrie Fisher?s disconnected performance context.
Han was a combination of Ben Solo?s memories and some force manipulation by Leia. (He takes the place of what would likely have been a Leia and Ben moment).
Rey?s parentage is less an undo and more of a redo. The seeds of this are in the first film. Even in TLJ Luke believes there is more to Rey?s origin, repeatedly asking, ?who ARE you??
I'm not sure who did what or how that balanced worked, but I place a lot of blame on Terrio's involvement (maybe unfairly so).