As someone who doesn't use kraken very often, but had to deal with a lot of them, I agree with
@Hari Judari. Most of the time the only thing a Kraken does to me is make me retreat, and if it follows me I usually kill them right after they transform back into a squid, I feel like if the knockback is too strong it might become "useless", it will still be able to catch squids from behind/off guard, but using it head-on like most people do now won't be an option at all.
While it's true that Krakens sometimes can only force you to retreat, I feel like that's exactly why it's being nerfed, because retreating is one of the only things you
can do in response (along with simply hiding, which you can't always guarantee to be safe if they popped the Kraken close to you to begin with, and using an invincibility special of your own, but most weapons don't have that). It's essentially a very powerful "line-breaker", one that has very few viable ways to directly challenge it without being forced to give up your position, which is very important in any shooter. Whether it's powerful to the point that it could be considered "broken", I personally don't think so, but I'm willing to bet Nintendo has noticed just how popular the Krak-On Roller has become purely because of its special and is making these changes to prevent any sort of over-centralization.
The other changes are interesting as well. On the topic of over-centralization, we don't know yet just how much the Ink Resist shoes are gonna be changed, but I'm hopeful it'll be noticeable enough to warrant using other shoes. Granted, I also never considered the ability's effects to be universally useful (save for the reduced DoT in enemy ink), but again, this is most likely an attempt to nip any possibility of over-centralization in the bud. However, the Ninja Squid nerf is a bit puzzling considering that Cold-Blooded is arguably better, especially in public rooms, but maybe Nintendo realized (belatedly, admittedly) that the speed difference was way too small to be considered an actual "drawback". Stealth Jump falls in the same boat here.