Wsj is only one magazine, jump has many other magazines with less popular series that are surely less competitive.
I don't see how cancelling a failing series is throwing the author away when they can still come back and try again a few times to get a hit.
The rest of the magazines may act differently, but jump is number 1, can't really say their system is bad in that regard if they are doing better.
The whole point isn't about cancelling what is failing, but the whole ruthless practice of Shonen Jump regarding veterans, and what is a failure depends a lot, the thing with SJ is that they're like a slave of their own system, you can sell more than enough to survive well in any other manga magazine, but if you're not doing well in the rankings/surveys they just cancel your manga doesn't matter if is a newbie or a veteran.
Isn't just as easy as "try again", there's a reason why so many popular authors that started on Jump never had anything more in the magazine, it's because the system, they want to treat a author that gave a lot of money to them like they treat a newbie that just started now, put these authors again under the pressure of having to go well in surveys and sell a certain amount of copies, if not maybe you will get 30 chapters and bye bye, seriously, who would want to get back after this?
It's how Shonen Jump works but isn't because they're the number 1 of that it makes the best system because even Shonen Jump is slowly changing and lowering their standards of sales.
...But this is about growth and popularity, not hard sales? Kimestu and Act-Age started small, but they had enough fans to where they were kept and allowed to grow. A series which is only running on past loyalty and not investment of the readers themselves is failing, it might technically be selling better than some, but only because of the past, not the future like Jump wants.
Also, what on Earth does this have to do with not giving extra passes to veteran authors?
You don't really get, i'm not talking about SJ publishing veterans for years just because a name, if the manga really doesn't sell, they're gonna be cancelled or quickly ended even with the author being well known, the thing is Shonen Jump system is naturally a bad fit for veterans, it forces SJ to be ruthless with authors that gave them money and popularity just because the series isn't selling at the standards that they created or because isn't getting enough votes, Shonen Jump has a long history of bad and disrespectful treatment with their big names because of this "ultra competitive" envoirment they created, to the point where you can have the crazy talk about Masashi Kishimoto possibly being cancelled because isn't "selling that much" or isn't "doing so well in the rankings".
Your logic about "failing" is nothing more than something based on how Shonen Jump works and their standard, not how the rest of the magazines works and their standards to what is or not a failure.