As succinctly as possible:

Disney paid a billion dollars for a franchise people cared about. It doesn’t matter what the franchise was or anything else, what mattered is that people cared and many considered it to be culturally significant.

Disney then made a trilogy without a long term plan other than “make a trilogy”.

The writing was at best lackluster, at worst laughable. Specific examples abound (“somehow, Palpatine returned”) but the major problems are that the core conflict of the middle film of the trilogy was contrived and the third film then had to scramble to cover the glaring, obvious problems. This writing issue eclipses other (still very serious) problems like a lack of character development with the main character, setups without payoffs, and trivializing or bastardizing supporting characters.