You're 100% correct. I have no idea what's going on with this man, but he seems to be just incapable of... I don't even know. Finishing the job? Kaguya's last third was a continuous dumpster fire with a straight up trash ending, oshi no ko seems to be going nowhere, and now this... thing of a manga. No structure, half of plotlines forgotten, I have no idea what it was supposed to be about.
At this point I'm just wondering how did he manage to write Kaguya, objectively the best romcom (up to a certain point). He's a fraud, but a bad fraud in that sometimes he writes straight up fire, and sometimes... Renai Daikou
Kaguya was basically gag manga filled with story in-between - that's why it had almost 300 chapters. If you'd remove all the joke/meme chapters and bits, you'd be left with less than a quarter of a proper, relevant storytelling. You can especially see that at the end, where he simply wasn't too keen to prolong any further this monster of a manga (in terms of size), so he "focused" straight on a story. And how it came to be... Well, we all know.
Similar case was/is with OnK. The beginning has similar structure to Kaguya, where plot is intertwined with a lot of gags, irrelevant shits and giggles. It gave him time to think, sort and react to all ideas that were in his mind, sifting through bad ones and throwing mostly good ones. But it didn't last much longer, because at some point (roughly when Renai Daikou was released) Aka started including only story in his work, without anything between. Maybe he has personal problems, maybe he's burnt out, maybe he's scared of creating another almost 300 chapters long story, idk, but instead of delivering well thought plots, he's wandering around some rough ideas and try to sell those as "finished product".
OnK has this advantage over Renai, like I wrote in my earlier comment, that it has background from times, when he was into that kind of writing, so for some time he had something to work with, buy at this point he's out of those strong points and have to rely solely on what he'll create "in a pinch" - which is working like... well, it just isn't working anymore. Renai didn't have that kind of privilege, from the start it was created as 100% story-focused title, and just after ~5 chapters many people could see, that it simply won't work. Thus it's comparibly low popularity and score.