The story itself was rushed. The culling games were boring af with a bunch of losers nobody gives a fuck about. What's fun about tournaments is seeing characters we like fight through them with compelling characters.
Culling games could've been pushed back deeper into the story, and develop the characters more before hand
That is why I think JJK is missing the worldbuilding to make us actually give a shit about these one and done characters.
Flashbacks arcs are not an absolute necessity, but they're very powerful tools in a visual medium. It is easy to transport the audience to different periods in time and it would seems pretty prudent to do in a series that constantly refers to the Heian era as this "you had to have been there" period, and constantly references the past in general. The Gojo flashback arc was good, I don't know why it was the only one like it.
Sukuna lore in particular isn't being given much chance to matter. Sun, Moon and Stars Squad and Five Empty Generals? Who gives a shit? I certainly don't.
Gege hasn't cared to show us, so why should we?
Let us not even get started on these empty cardboard houses that are the sorcerer clans. The Gojo clan is apparently a one-man band. No word on who raised the one we know or whatever. Sugawara Michizane, who? Big Three Vengeful Spirits, what?
Wafer thin worldbuilding.
And it's extending to the fights as well. Gege just loves to break his own rules. It's like he writers himself into a corner for a challenge to see how he can come up with discardable solutions to his own problems.
I quite like JJK, but I'm certainly not wowed by it as a whole. Gege's biggest strength is in characterisation. Whatever else I have to say about it, it's impressive what kind of cast he has managed to build in such few chapters. Building that kind of connection with the audience does not happen by accident.