Top-tier talent usually know their worth, and thus would demand more money, more creative freedom, bigger royalties, and possibly some creator ownership. All of that is the antithesis of the big two's business practices.
Image is the best example because it was one of the few times Marvel actually tried to keep talent. They were paying Todd McFarlane, Rob Liefeld, and Jim Lee a million dollars, each, to work exclusively for Marvel, only for them to demand more ownership and jump ship. Marvel got burned and got back in line with the industry standard of treating talent as completely disposable.
Either way, it's irrelevant. The comics market is so bad that they'd be like parasites trying to suck blood from a dead cow.
Slott, Waid, and others of upper editorial aren't some danger haired bisexual college student who wants to write about trannies. They're industry professionals. They've been in comics for decades and have managed to survive long enough to be successful. They might be left-leaning, they might espouse social justice views, but when it comes to their job, they're going to focus on trying to sell comics. The sjw shit is not going to be a hill they're going to die on. Especially when you consider the down-turn in Marvel Comics cost the editor-in-chief, Axel Alonso, his job.
As for the HR departments, social media, and comics news, they're all jokes. HR in comics is virtually non-existent, social media only matters when comic shops care about it, and comics news wishes they were relevant, to the point that they've tried several times to create a "comicsgate" of their own.
Again, cancellation threshold is based on two significant numbers: the number of units sold and the issue number. For example, America #6 sold 9,548 units, which is above our current estimate of Marvel's shit-canning number of around 6,500.
You also have to understand that Marvel puts out so many titles a month that the lower selling comics start to pay for themselves and generate pure profit. The sheer amount of comics DC and Marvel are able to throw on the market is why they're the only companies that actually profit from floppy comics.