Mostly you have to add things before and after the films.
Let's say that we learn that Luke did successfully train several new Jedi before going into exile, and those Jedi were off world when Ben turned to the dark side, looking for their own students to teach. Suddenly Luke's not such a failure as a teacher. Let's say part of why he went into exile wasn't just because of what happened with Ben, but because he realized he was training the new Jedi just like the old Jedi were trained (including him), and he was unintentionally setting the new Order up for the same flaws and failings that took down the previous one. Suddenly Luke isn't being a selfish jerk for leaving, he's making a noble sacrifice by removing his influence, allowing the new Jedi to grow beyond him and his legend.
Let's say that after the sequels, Finn begins training in the Force and helps rebuild a new Jedi Order. Makes up for a lot of his treatment in TLJ and TRoS right? Alternatively he could become a big, important general and military leader for the next government, if him becoming Jedi isn't to your tastes. Hell, do both!
Let's say that after the sequels, Rey never mentions Kylo again and begins a new adventure building the new Jedi along with Finn. All the toxic crap with Kylo still happened but it's never mentioned again outside of maybe a few jokes about Rey having bad taste in men.
And doing that with Luke, Finn, and Rey also gives you two different Jedi factions to play with, should anyone be interested: the orthodox Jedi who Luke trained and the new Jedi put together by Finn and Rey.
Do some flashbacks that flesh out Poe's relationship with Leia (TLJ set them up with a mentor/student dynamic that Fisher never got to delve into), and then have Poe help rebuild a new government in her honor and memory. Now the new New Republic is made in Leia's image, a worthwhile institution that makes Leia look great for being its inspiration, and it enriches Poe's story as he transitions from soldier to politician.
The Clone Wars show was able to salvage the awful prequel movies by adding stuff between film Episodes. The sequels are too squished together to do that but you have decades of unexplored history in either direction to work with, and the revelation of something happening in the past can provide new context and understanding to events in the sequels while stuff that happens after can course-correct them.
Hell you could even justify Rey claiming the Skywalker name by revealing her mother was somehow related to Anakin and Luke. An aunt or cousin or something. That adds some context to her connection to Kylo as well as her natural affinity for the Force, and genuinely puts the Skywalker bloodline back in play, rather than having someone from the rival family co-opt it undeservingly. Sure, that doesn't entirely make sense and it's a tad convoluted, but climbing out of the mess the sequels made will require a few concessions.
Hell, if Rey were revealed to be an actual Skywalker it'd even keep with the franchise's habit of making family members kiss!