Haven't had a chance to see the episode, but the premise sounds great (needing to save a historical monster for the greater good and all that). However, the new show runners obsession with retconning the Eugenics Wars makes no sense to me; none of the arguments have "justified" why retconning the date to keep the franchise from having past events different from our's is needed, esp. since only destroys the pre-established timeline for literally no gain beyond them being able to say: "Hey, it happened in the 2030s now!" It does not make
Star Trek any more aspirational than it was before, nor improve the storytelling, and only undermines the tales it's trying to build off of.
Also not sure that having be part of the story that the timeline was changed in-universe makes the retcon any better and might just make things even worse. Pre-SNW, the model seemed to be to just ignore the spoken dates r.e. Khan and the Eugenics Wars and pretend that the characters had said something else (or go for the "fragmentary records got stuff wrong" idea if you needed more than that). It makes hash of the old stories and means we can't understand the story the way it's told, but numbers and dates are easier to fudge than other stuff and it's simple enough. (Also, it was vague enough that fans who didn't want canon broken didn't have to follow it.)
However, now, with it being part of the story that history was changed, the only logical conclusion is that SNW (and the other post-DSC shows?) are now part of an alternate timeline separate from the original prime universe as we know it (TOS/TAS/TNG/DS9/VOY/ENT/movies 1 - 10). Granted, an alternate timeline might explain some of the broken canon stuff (like the Disc-prise vs. the TOS configuration, "Horbus" vs the Romulan sun, the reimagined SNW Gorn vs the original Gorn, etc.) -- although that does create its own issues, since PIC and LDS only make sense in context of the prime universe 1.0 that SNW is ignoring.
I have liked most of the modern
Trek shows as sci-fi shows and am looking forward to catching up on SNW, but I do have to completely divorce them from from the classic stuff to not be bugged by how revisionist the shows are. I don't think the "have their cake and eat it to" take to canon (for all intents and purposes, the show runners want the programs to be both sequels/prequels and reboots, but without the drawbacks of either) is working; the franchise's internal world doesn't make sense anymore when you piece everything together.
Honestly, at this point, I think they should just come out and officially make modern
Trek a parallel universe branch of the franchise ("prime universe 2.0"?) that branches off the main one somehow; that's the kind of series they're making, so just own it.
Let's just say I'm old enough to remember when Iron Man's origin involved Tony Stark being captured in Nam by the Viet Cong. And when Captain America was traumatized by Watergate, after being unthawed from the ice in . . . the early 1960s. And the Hulk was created by . . . an outdoor nuclear-bomb test in the New Mexico? You know, the kind we have all the time these days.
Marvel Comics have always operated on a sliding timescale in terms of current events, so that exactly which conflict Tony Stark was injured in keeps being moved forward. Ditto for what wars Nick Fury fought in.
And, of course, to explain why Spider-Man isn't collecting Social Security Payments after being a high school kid in the 1960s.
I don't think that's a great analogy; the Marvel universe is a floating timeline with no set end for any of the characters; the
Star Trek universe has been fixed for years with characters' stories having endings.