They add context but can be safely skipped while still understanding the review.
Review in brief:
White Fox, wanting to show the world that Steins;Gate 0 would be adapted into anime, decided to go the extra mile and made this alternate version of Steins;Gate episode 23. While this special was carefully made to blend in with the original episode and give a subtle peak at what’s to come, it forgets one very important thing: to properly cement itself as an ending of Steins;Gate.
Review in full:
I've always seen episode 23 as one of Steins;Gate's best episodes. Re-visiting the events of episode 1 and revealing just how much was actually going on gave credence to the sudden turn of events at the end of episode 22, and Okabe mustering the strength to try one last time to set things right despite all that he had been through was one of his defining moments. Heck, what Okabe ended up having to do led to what was perhaps the most defining moment of the entire story. The reason I consider Steins;Gate to have a good ending, or even an acceptable ending, is because of how episode 23 played out.
Of course, the reason this alternate version of episode 23 exists is to show where the path splits to allow Steins;Gate 0 to happen. It certainly looks and feels like it came straight out of the original show despite being made four years later, and considering the original's quality it's impressive that way. Whether Steins;Gate 0 changes the artistic style from this point is to be seen, but what’s on display here cements it as being just as much a part of this Steins;Gate as it will be a part of the next installment.
For that same reason it's somewhat understandable for it to reuse 2/3rds of the original episode 23, but it doesn't leave itself much time to show the difference. Maintaining the old episode until the path splits gives it authenticity, but it should have allowed itself to be longer than a standard episode to fully explore its alternate direction because it leaves a few gaps in its wake. It ends up feeling like a partial showing, one that was meant to create confusion rather than provide resolution, and considering the time skip it contains there’s little chance that Steins;Gate 0 will clear things up.
Spoiler, click to view
First of all, there's no particular reason given as to why Mayuri decides to comfort Okabe after his failed attempt to save Kurisu instead of snap him out of his depressive state like she did in the original. Every other time different events have occurred at the same point in time in this series (aside from Okabe meddling with them using time travel of course) it's been across two different world lines, whereas that isn't the case this time. Meanwhile Suzuha does nothing to change what's going on despite knowing that the failed first attempt was necessary and that future Okabe was going to send a message to the past with further details (details she seemed to have known herself even!)
The high audiovisual quality and attention to key details in this scene give a glance of just how powerful this alternate episode could have been if it was cohesive throughout.Despite these unanswered plot-holes, this special nails the sense of failure Okabe initially finds himself drowning in. His loss and regret are strikingly portrayed, and it only took a couple scenes to convey this thanks to the ever-well coordinated and fitting visuals and sound work. Then, as depressed as Okabe is that night, we don't get to see how he brings himself to (partially) recover in the next month or two, which is a shame because Okabe simply doesn't receive the extra development he did in the original (and for that matter Mayuri didn't either since we already knew her nurturing side.)
We get to see what Okabe became as a result of this alternate experience, which is important in its own right and got the attention it needed, but without a smooth transition it ends up looking like Okabe suddenly wiped his memory to alter his habits instead of consciously changing himself as life continued around him. With no indication that he intends to revert back to the way he was before, the episode as a whole comes off as incomplete or unintentionally cut. Of course fate might have other plans for him, especially with how this special ends (or rather teases the beginning of what’s to come) but the unnatural presentation of Okabe’s self-change still left a sour aftertaste.
Verdict:
I can appreciate this special for how it bridges Steins;Gate to the new story to come but I’m not pleased with the one-way nature of it. By lacking the story detail needed to provide proper closure it fails to be the keystone that the original episode 23 was to Steins;Gate. It works well as Steins;Gate 0 episode 0 but it’s not a proper ending to Steins;Gate despite containing the plot and production values to have managed it with the proper direction & length. By both showing Okabe try to leave this special’s events and not showing what led him to that course of action, episode 23 β forgets some of the elements it needed to be cohesive and comprehensive, even if the rest is well-presented.