Eh, JJ doing 7 and Rian doing 8 was fine. JJ continued to work on 8 and Rian was involved with 7, so it’s not like there was a hard reset between each movie like some people think for some reason.
There are several discrepancies between TFA and TLJ. And JJ had little to no creative input on TLJ (though Rian had some input on TFA).
At the end of TFA, Finn is severely wounded by a slash to the spine that puts him in a coma as a result of standing alone against a dark lord to protect his friend. In TLJ, he wakes up comically, his body completely fine, then is portrayed as a selfish coward in the following scene. He is then demoted from lead character to side character sent on a filler quest.
In TFA, the First Order is a fringe faction launching a surprise invasion of the galaxy. In TLJ, despite having just lost their most important weapon, they are abruptly put into the position of “established galactic government,” essentially making them the Empire again. (TRoS then nerfs them in order to make Palpatine’s fleet seem to matter.)
In TFA, Hux is a serious, calculating, but passionate military leader. In TLJ, he’s a clown.
In TFA, Snoke is portrayed as mysterious and imposing, someone commanding from the shadows, and the film ends with him resolving to complete Kylo Ren’s training. In TLJ, we see him in person with no real fanfare, and he looks like a cartoon villain in a golden bathrobe, who pettily mocks Kylo for his failure. He later orders Kylo to kill Rey while she is being held down and defenseless as a completion of his training, despite him just killing his father, which would have been much more difficult and significant for him.
Luke is shown in Jedi robes, then immediately changes out of them in TLJ.
Rey’s backstory is built up as a mystery, then cast aside as unimportant. (I admit it’s possible that “Rey Nobody” was always meant to be a misdirect to save the true parent reveal for Episode IX. But I can’t say for sure.)
And TLJ ends in a way that essentially felt like an epilogue. So many plot threads were cut off that Episode IX was bound to feel like a reset and be disconnected from the first two films. It also doesn’t help that neither Kylo nor Hux was a strong enough villain to serve as the main antagonist in the final film (and Lucasfilm seemed set on making Reylo happen, so Kylo had to be redeemed somehow, anyway).
The sequel trilogy could’ve been made more cohesive if there was one central vision behind it, but after the prequels I don’t think that would’ve been a good idea. Better to keep it as a group project, but, you know, not toss out the most important third of your trilogy.
I don’t think we should cast away the whole idea of a central vision just because George botched the prequels. The main issues with the prequels lie more in their execution (dialogue, acting, tone, character personalities, special effects). But the overarching story of the prequels has good bones. The issues with the sequel trilogy are on a much more fundamental level. The overarching story of the sequels was broken and built on a faulty foundation from the start. The sequels mostly nailed the more surface-level aspects of filmmaking that the prequels failed at, but that’s not enough to redeem a story that fundamentally doesn’t work. A clear vision of how to continue the story post-RotJ was desperately needed. You can’t make sequels to some of the most revered, classic films of all time by just “winging it.” If there was ever a sequel trilogy to Lord of the Rings written in a similar manner as these films were, they would be despised with good reason.