Few things to address here as someone who works a lot in the film business --
Scott staying on as an EP means absolutely nothing. It is the bare minimum extended to someone who worked on a project, even if they were fired or quit. Often, it's contractual. It's likely that from this point on, he will have zero involvement in the film other than possible attendance at the premiere and informal advice to the new director, should he be directly asked and choose to give it.
Scott previously tweeted in December, quite cryptically, that "release dates are the enemy of art." This was the bellwether that something was afoot. Maybe the script isn't ready. Maybe Disney won't give him the production time needed to realize what he's proposing. It isn't clear, but there were clear signs Scott was unhappy with the present release date.
Yes, Disney has had a number of recent, ugly, and public director breakups between Edgar Wright's Antman, the Josh Trank Star Wars, spin-off, Star Wars Episode IX, and the Solo debacle. Phil Lord even congratulated Scott for joining a "club" on Twitter after the news became public. This most recent development points to it not being a Lucasfilm-specific issue, as has been previously discussed... it may just be at the hands of broader Disney leadership.