Honestly, it all hinges on one decision. I like to think I'm a pro at playing out "for want of a nail" scenarios (😏).
And the nail in this particular scenario is Stiles.
I find it very strange and honestly OOC for him that he just. Leaves Erica and Boyd with the Argents. Says and does nothing about it. Yes, I know, we all like to point out that Stiles suggests murder as a solution often, but honestly, when he does, it is a legitimate solution to their problems. But Erica and Boyd aren't a problem, and even if they aren't friends, they aren't people he'd leave to be tortured and more than likely murdered by the Argents, who probably aren't his favourite people in any situation. And yes, I know, his dad, but here's the thing. The Sheriff is worried about him, a given. But physically, the Sheriff isn't at all in harm's way. He might be stressed, but him being stressed about Stiles is not new. Erica and Boyd are in real, immediate, physical danger. They are, at present, hooked up to a power source and being continuously electrocuted and held hostage by Thee family of werewolf hunters who have a disturbing record of ignoring their so-called "code" whenever they feel like it and aren't above killing innocents, humans, and children.
And we see that Erica and Boyd aren't being watched in the basement. When Stiles is put down there, it's just them, same when Chris comes down later to let them go. I'm sure the house itself is guarded, but they don't have eyes on them at all times. And Stiles canonically makes a habit of breaking into places he shouldn't be.
Granted, if he did go back and get them out (I'm not talking about a fight, I mean flat-out booking it bc the Argents aren't stupid enough to open fire in the middle of their own residential neighbourhood), maybe Erica and Boyd wouldn't go with him. It's not out of the question. They were leaving anyway. But imagine how. Galling. it'd be, to be a werewolf, stronger and faster and able to heal from mortal wounds, a creature right out of myth, and be shown up by a human. Not saying they were 100% wrong for running away. There were bad decisions being made all around – them, Derek, everyone. But Stiles is the same age as them. He's human. And he's staying in the fight. He doesn't have to. He could've just gone home. But he came back for them, even after they've been antagonistic towards each other. And he's going back still after being beaten by Gerard.
Maybe it's pride, maybe it's shame, maybe it's an instinctively, impulsively formed pack bond. But I think they'd go back with Stiles.
But here's the next layer. If Stiles isn't home, there's no one to bring Lydia. The whole deal of her going to Stiles to cry about Jackson's "death" makes no sense (why wouldn't she be with Danny, Jackson's best friend and one of her actual friends? Instead of the weird guy who behaves so creepily and inappropriately towards her and who also does not like Jackson, was bullied by Jackson, and was under a restraining order filed by Jackson for kidnapping him?), other than the fact he's literally the only other available character who can bring her in. Scott, Isaac, Allison are all preoccupied with the Kanima, same with Derek and Chris, and no way in fucking hell would she go anywhere with Peter. Even if Stiles is "in the know", Lydia's made a point that she does not want to be in the know. She doesn't want to be involved. But The Plot has to happen and Stiles is all that's left, so they just huck her to the Stilinski house, forget logic.
But no Stiles means no Lydia means no magic miracle cure for Jackson.
Not saying that the cure wasn't a cool reference to werewolf lore (calling a werewolf by their Christian name was a "gentler" myth of curing them, along with presenting them with their human clothes), but it also had notes of deus ex machina, IMHO. The whole season has kept up this Scott vs Derek sub-arc, Scott being the "right" one for wanting to cure and save Jackson, even if that means many other people die in the meantime, and Derek being the "wrong" one for wanting to kill the legend-even-to-werewolves, nearly indestructible, mind-controlled creature whose sole purpose is to kill and can't be reasoned with and is about to evolve into its Even Worse form, even though him/his pack are being blamed for these deaths and being wrongly hunted for it. And it's their contrasting attitudes towards this situation (saving one life no matter what vs taking one life to spare how many more) that make the cure feel like. Something of a cop-out. Rewarding Scott for all the shitty things he's done by adding a little "I told you so" on top about curing Jackson, and reinforcing his stance about there always being a "moral" solution. Which isn't feasible or realistic in any way. Sometimes all the options are shit, and making the hard choice is necessary. Even Derek acknowledged that! He tried to take the cure path too, when it was an option! And look where it got him!
But imagine the fucking satisfaction of having Stiles come in, metaphorical guns blazing, with Erica and Boyd instead. And the Kanima was already this close 🤏 to evolving, which was the Whole Point of them scrambling the past two episodes—they are out of fucking time. The Kanima is about to turn into something bigger and nastier, with goddamn wings (which means it can't be tracked on the ground, that it has an avenue of escape none of them can follow), and it is being controlled by Gerard fucking Argent. Matt the Rat was a petulant teenager with superiority problems. Gerard is a goddamn sociopathic serial killer who has no issue with manipulating his children (where do you think Kate got it from?) or his granddaughter, even killing them to get what he wants, and has been shown, multiple times, to not have any semblance of morals, empathy, kindness, anything. He killed an Omega in the first episode just because he could. He said out loud in his introductory speech that he was going to kill any werewolf he found in Beacon Hills, innocent or not, just because he could. Gerard is not someone you roll the dice on, and he is not someone you leave in control of a nigh indestructible monster like the Kanima.
And instead of the....Everything that happens with Scott and Derek and Gerard (I will never be over it, McCall can McCatch these fucking hands), we get the first real incident of the pack acting like a pack. Instead of seeing the Argents work together better than the literal pack animals, we see the werewolves bringing down something bigger and badder than them together.
And tbh, I wouldn't have been that upset by Jackson dying for real. As far as everyone else is concerned, he's already dead, and he wasn't that likeable. Sure, he had his sympathetic moments, and there's times I felt bad for him, but he was still an entitled asshole who begged, bribed, and blackmailed his way into getting the bite because his ego was just That fragile. If he'd stayed around and got some more development, showed some growth, it'd be different (IIRC, Colton Haynes left for personal reasons, no issue with that, I'm strictly talking about the character, not the actor), but we didn't get that, so he's just a somewhat sympathetic bully who got his lycanthropy, his cure, and then got to leave and fuck everything else, which is nowhere near satisfying. And him being a Kanima/werewolf hybrid was so fucking stupid, don't get me started.
But if Jackson had just died and stayed dead, it still could've been sad. Sad because he was still a kid who didn't deserve what he got. Sad because he did have friends and parents who cared about him and will mourn him. Sad because he can't grow up and be better. And it could've also been a wake-up call for Derek that he needs to do better as an Alpha, for the Betas to do better as his pack, for Stiles and Scott's "friendship" to get some much-needed adjustment, for Scott to maybe (but probably not) learn something about no-win scenarios and taking the path of least bloodshed instead of some unrealistic moral high road.
And the Alpha pack would still be a problem! They still have Cora! Maybe they snatch Isaac instead of Erica and Boyd, and since Isaac has no living family, it's on the pack to be looking for him (I still feel robbed we never even saw any other Reyes or Boyds) because they're the only ones who can. And I think it'd do something for Peter and his relationship to the pack as well, seeing the foundation of something with real potential, real possibility, a chance to get the Hales' star rising again.
All because of one dumb decision.