Ehh, it was more than just one film. The entire sequel franchise has been one misstep after another. TFA wasn't all that great, it just had hype running through it and normalfags wanting to be hip with "The New Best Thing" for that year, and ultimately forgot about it once other movies and shows lured them away.
You had Disney wanting to milk this franchise for decades to come and them making the decision to make a Star Wars movie every year, for the foreseeable future(a decision they now regret due to the Solo flop and have now shuttered Anthology movies). They saw dollar signs and wanted to make a quick buck by shoving nostalgia up everyone's ass.
Lucasfilm cared more about identity politics, rather than creating a good movie series. They didn't even have a plan for their overall Sequel Trilogy and allowed the hacks JJ and Rian to create a very poor series of films that ultimately made the OT a joke and the formerly happy ending to be torn down and destroyed, just to make a Not-Empire vs. Not-Rebels fight each other with the same weapons we had before(Just for nostalgia points, once again)
Wendig's series of books were utter garbage, but unfortunately they were the foundation that was laid down. Thankfully he was fired, but the damage is already done.
Then you had fanboys who shoved out Lucas and made the creator of this whole franchise quit wanting to make anything for Star Wars ever again and sold it to the soulless corp. named Disney.
It wasn't just one movie, it was the end reaction of several elements that when mixed together turned this whole thing into mess it has ultimately become.