The previous Zero-One Others film is just a setup to this entire film, and once all the setup is out of the way, we are in for a treat. If REALxTIME is the series' true ending, the Zero-One Others films is the series' epilogue, and it's final statement about its message about AI & machines, and what is the true meaning of "justice".
It's bittersweet, yes, but this how they want to move forward. This is, surprisingly, one of the most mature ends the series had. Last time I experienced this kind of feeling was with the final episode of Kamen Rider Blade. Bittersweet endings are fine especially if the lesson hits close to reality. To put it simply, I really like this movie.