There are many theories as to why the Star Wars fandom is so upset with the Last Jedi movie and it all comes down to mindset!
Much of the anger stems from the old way of the Jedi teaching being disregarded. Luke and the next generation of Jedi are forced to figure out a new way to use the force and become Jedi.
Luke Skywalker failed to teach the next generation of the Jedi and felt as though he triggered some to move the dark side. He was using the same methods that had been used by the Jedi for thousands of years. So when this method failed, Luke believed that the Jedi should end the force forever.
This changed when Yoda appeared and espoused his belief that failure was the greatest teacher. He brought down lightening and destroyed all the old Jedi texts, which he declared “page burners they are not.”
Now there would have to be a “new way” of teaching the Jedi. That new method embodies the principles of growth mindset:
Accepting failure and learning and growing from the mistakes made.
Understanding that there is more than one way to learn a concept.
Praising effort as opposed to results.
I believe that this change in the mindset of the Jedi will provide great results in the future Star Wars installments.