I never put any stock into what corporate types say. To them firing an executive is a big task and hit, but hardly something they'd balk at if it was the tight move.
Again, I don't think Kennedy has underperformed Disney's expectations, in under a decade her films recouped the buyout of Lucasfilm, and her shows were basically the main reason to get Disney+. Not to mention highly successful Disney TV shows too, especially Rebels. And a revamped interest in the books.
Taking those stories though isn't that easy. You have to have the rights. Even if they brought Thrawn in, if they did Heir to the Empire they'd have to pay Zahn. Keep in mind as well, though Zahn's books were great, many EU books were absolute trash. Lucas gave a model for adapting EU into film, by borrowing parts of it for flavor and making your own tale.
I hate that people pretend that the EU was canon. BTW. Lucas himself said it wasn't canon, it was it's own universe. Kind of like Marvel's multiverse.
They had Lucas's outline, that was it. They took inspiration from that outline.
It isn't comparable to Marvel, they have classic comics and arcs they can draw influence from.
Wandavision - heavily influenced by House of M
Thor: Ragnarok - Heavily influenced by Planet Hulk
Iron Man's origin and Iron Man 3 are from Extremis comics.
Winter Soldier - Based off the Winter SOldier run
Now, I could go on. But I don't care to. Marvel has existing characters who need to be filmified, they don't need to wholesale create new characters and introduce strife to existing ones.
Don't get me wrong, I think as a whole the sequels failed. I think it could have been an interesting experiment in baton passing, if 2 things hadn't happened.
First the shoehorning of Rian Johnson by having episode VII end with Rey meeting Luke. Movie should have eded on the map to Luke. That gives the next director time to decide where they want to go with the story. Instead JJ was basically shoehorning Johnson into starting the next movie right away. But the main problem is Episode 9. It not only retconns the first 2 movie of the sequel trilogy but the whole star wars saga. Anakin's sacrifice in Ep 6 is meaningless. WHole plotlines in books are thrown away, Creating Sith Wayfinders and Dyad in the force to do things that JJ wanted to do. Lightspeed skipping and TIEs tracking them thought hyperspace (remember the whole subplot to lead tracking from the last film) death star tech on Star Destroyers. It's a literal funk any any and everything Star Wars.