There are probably a million and one "writers" involved on these projects who all want their fingers in the por so coming up with anything new that doesn't have the corporate mass market seal of approval is likely a pretty laborious process. And unlike the Marvel movies you can't just come up with episodic content to fill up time and build to a structured finale. It was easy then, pick a hero, pick a villain, pick a plot, good to go. The whole thing has already been written for you, at some point in history. Star Wars doesnt work like that. Well, it could I guess, but in ditching the EU so they wouldn't have to pay anyone for their ideas they limited themselves only to either Lucas's stuff, or their own. And they've squeezed literally every ounce of juice they could out of the former. So now you are in boardroom creative hell.