It is ultimately her direction and final say which has resulted in bad sequel trilogy. Not having a set plan from day 1 was a mistake. Her hiring and firing of directors doesn't give a good impression on her judgment skills. She said she wanted to "protect the characters that Lucas had created and intended" yet she's responsible in the end for butchering them. And after all this she hasn't seemingly learned anything.
2) The sequel fans
Sorry, but people who elevate the sequels way beyond that which they are, are a big problem and give Kennedy the picture that what she's doing is perfectly fine when in reality it is not. All 3 sequels have made good money so its not that boycotts and stuff are relevant. Mainly its the fanatical sequel fans with the "dont criticize, consume product" mentality that has caused the divisions. The Disney shills like Collider crew are a great example.
Disney for buying the rights off Lucas (and him selling them to Disney by extension). Tearing apart the EU cannon, making movies that are risk averse and trying to copy its own successful Marvel entity by inserting many features into SW that were never going to work.