I think it's because of the novel Heir to the Empire in the old EU.The term Gray Jedi, or Gray, had two meanings. First, it was used by Jedi and Sith to describe Force-users who walked the line between the light and dark sides of the Force without surrendering to the dark side, and second, it described Jedi who distanced themselves from the Jedi High Council...starwars.fandom.com
The first movie was in 1977. This means in 2027 will be the 50th anniversary, and after it's enough time to allow themself a reboot.
We have other option: The prophets and seers who can see the future are canon in SW. This means someones could see different futures, and then Disney could publish a new serie about these "prophets' files" where a group of arcaheologists search a old holocron with the files of these prophets. These files were created by the cooperation of the prophets seing the different possible futures, and telepath reading the mind and sending those mental images to a "holo-scribe", other force-adept with telekinetic powers being used with holograpic technology to "record" those prophecies as 3D movies. This trick would allow to be canon but alter the canon and almost nobody would be angry. An example of alternate timeline would be the galaxy for the age of the Rakata infinity empire being conquered by the yuuzan vong.
* SW is a fabulous franchise, but after the batle of Yavin (the first Deathstar is destroyed) almost all the main events in the galaxy are linked to Skywalker family and company. And jedi may have got too much prominence.
Star Wars was basically dead and it started the revival in the 90s. Everything since owes it's existence to that novel.
It was the sequel to RotJ. It it remained that way for 23 years.
Even now almost 30 years later they've added elements of it back into the new canon.
For example Thrawn. He's a fan favorite shrugs.