I think I talked about this with you in PM's but Toriko was always depicted as a "fun" series and their ambitions were very simple, it was explicitly stated very early in the manga. Which is why I find this "weak character writing" to be a pretty lousy criticism for a series like Toriko. Sure it could've been beneficially but it's not a necessity for the series to have it. I don't think Toriko readers expects some great character writing in a series where everyone is driven by appetite. People read Toriko for its world building aspect and the hype/manly art/creativity/fights are a big bonus. That's the selling point of Toriko and it hasn't changed for pretty much the entire run of the series so why would it likely fall off if the anime was to adapt it?
It's sorta the same with CSM; after reading the first few chapters, I didnt expect great character writing because the series already set its tone and I knew what to expect from it. It's a series that delivers a lot of hype/twists and aside from the MC being relateable (with some awesome SoL chapters), there's not a whole lot to brag about the series character writing yet its still adored by many for how hype/unpredictable it is.
You see, while I acknowledge that and know Shimabukuro's intention, I can't exactly say it's a justification myself. From reading Toriko, I found myself frustrated how Shimabukuro's attempts at cast building always fell flat due to the sheer scale of the setting preventing anyone from having meaningful interactions, and how Coco, Sunny and Zebra had very little in the way of character focus or development beyond "They get stronger". While you're entitled to not seeing this as a problem, I'd wager it was a factor that hindered the series after 2012 or so insofar as popularity.
The Chainsaw Man comparison is a contradiction. You say that the series character writing is average, then note that it has strong SoL chapters,
a part of the story which needs character writing to function. Indeed, the most remembered of those chapters, the Denji/Makima movie date, is just two characters
talking for 20 pages. Not about plot stuff, just general thoughts. That that chapter got so much discussion is objective proof that, in some way, the series has good character writing.
Lastly, Nakano himself has said that Jump's modern focus is "attractiveness of character", the idea that the main strength of modern manga hinges on its characters. You can see it with pretty much every modern Jump hit in the last ten years, and the vast majority of modern hit in the industry period. I struggle to see how Chainsaw Man is suddenly a massive exception to the rule, or that such a shift (likely built in part from the decline of magazines) wouldn't negatively effect Toriko.