I think the brand damage is overblown. 9 is more about whether or not TLJ did really alienate that many people. If it does around as well as TLJ or better, then the naysayers were wrong and Star Wars isn't in trouble. If it does considerably worse, then heads will roll.
I, for one, enjoyed TLJ. I think a number of people did. However, with the greatest of ease public opinion is swayed quickly today. FWIW, back in 1980 people didn't appreciate Empire Strikes Back that much. That was related in the critical review from the NY Times:
Published on June 15, 1980, Vincent Canby wrote this in The New York Times:
“The Empire Strikes Back is not a truly terrible movie. It’s a nice movie. It’s not, by any means, as nice as Star Wars. It’s not as fresh and funny and surprising and witty, but it is nice and inoffensive and, in a way that no one associated with it need be ashamed of, it’s also silly. Attending to it is a lot like reading the middle of a comic book. It is amusing in fitful patches but you’re likely to find more beauty, suspense, discipline, craft and art when watching a New York harbor pilot bring the Queen Elizabeth 2 into her Hudson River berth, which is what The Empire Strikes Back most reminds me of. It’s a big, expensive, time-consuming, essentially mechanical operation. The Empire Strikes Back is about as personal as a Christmas card from a bank.”
However, one of the most complained about aspects of TLJ was that it didn't explain every detail and dive deeper into characters backstory than R2D2 into a Degobah swamp. Yet, back in 1980 Harrison Ford already knew that there was the need for patience:
'Logical, given the film’s structuring as the second chapter in a three-act play, a point raised by Harrison Ford in the July 24, 1980, edition of Rolling Stone.
What people really have missed is how similar things with the continuation of this saga are to the original trilogy. Even more so, Disney is holding back to allow themselves to fill in more gaps with further movies, TV Series, books, etc. There are some flaws with TLJ, however no more than any in the original series. Most "fans" have simply lower attention spans and 'trained' expectations for how a movie is supposed to play out. It's a difficult thing to produce a trilogy in such an atmosphere. However, I have definitely enjoyed their efforts."One of George’s real strengths is not giving you all the information you need, yet at the same time not denying you anything essential. You have a feeling that you want to know more at all times.
“I have heard frequently that there is a certain kind of disappointment with the ending of the second film. I’ve heard people say, ‘There’s no end to this film’ or ‘I can’t wait to find out what happens.’ But they will, and that’s exactly the effect intended by the ending.”
That aside, SW:GE has a whole different set of issues that result from poor park management decisions. These decisions have been ruining many aspects of the parks long before this current set of errors.