I think the core of the problem is that like a lot of directors, Johnson didn't want to do someone else's work. He had JJ/Kasdan TFA before his movie, the Kasdan/Treverrow TLJ script already done, but he wanted to do his own thing, make his own name, and Disney were dumb enough to let him throw out what went before.
It's like he said "oh, don't want to do the Snoke storyline, kill him off, don't want to deal with Rey's manifest destiny story, bin that, don't want to do Luke as a messianic figure, throw that away, don't want to do Finn mortally injured, make him recover with no ill-effects in the first five minutes. Guardians of the Galaxy crossed with the new Ghostbusters? Michael Bay style with a Star Wars theme? Children's toys and merchandising? That's the way to go!"
This is so true, but you would have thought at least make it remotely close to the last rather then gut the entire plot points from the last movie. Its a continuing part. I am very surprised they dont have something like MCU, where they have people that know the material need to sign off before allowing this to go through. Disney has definitely dropped the ball in this one imo. Does that mean in future lets forget lightsabres and guse imaginary force sticks which are invisible and sharp (saving budget and effects). You can see how absurd it can go if no one is reigning in and get some sort of balance and direction in what they want to do. Its not pass the parcel ffs.