Aka is that kind of writer that is able to start a story and get you invested in it, but somewhere in the middle he loses his magic. I can guarantee you you can watch the first two seasons of the anime or the first 80 chapters of the manga, skip the next 81 chapters, reading the last 5 chapters and still manage to understand everything that happened. Why is that? Because the 5 arcs spread on those 86 chapters are mostly beating around the bush. Sure you get some development here and there, but mostly it doesn't make a difference for the outcome because Aka basically builds the whole story on those first 80 chapters and that's why he struggles with the rest, it is hard to develop a story that was already developed, so on the following arcs he mostly "goes back to the basic" returning to the entertainment industry that is mostly sidetracked, but it feels like filler, filling a certain amount of chapters his editor probably set him to do, I'm pretty confident this manga could have ended with 100, maybe 110 chapters - considering the content he officially released.
However, unlike Kaguya-sama, I managed to read the whole thing here in Oshi no Ko, so maybe kudos to him for "improving"? Still there's a long way to go, or maybe I am being to harsh? Maybe Aka himself wanted to ended this manga sooner, but he wasn't allowed to because it makes perfect sense - writing-wise - to have this story end 20 or 30 chapters after the 80th chapter and it wouldn't feel rushed, instead we got a story that gets really bad and a poorly written ending. I don't think it was even a controversial ending considering how most people hated it. So do consider that when reading this: half the story can be skipped and you would still be able to understand the ending, doesn't it make the quality of the writing here questionable?