I'm not versed in the source material at all outside of common knowledge for fans of the shared universe, so my enjoyment of this film is for the film itself. That, and the Tomorrowverse overall. Were I an avid reader of the comics and knew Crisis well, it would not surprise me to find myself disliking this far more.
But as a trilogy, this conclusion really wasn't so bad. It was greatly helped by brief visits to well-loved shows in the past, all in its original art style no less. The nostalgia train hit me so hard I couldn't help but instantly like this film a little more the second it came on screen. This movie also had some decent moments unrelated to old heavy hitters. While it wasn't the best of the franchise, I still enjoyed it for what it is.
However, the main issue with these recent films is that hardly any of them are complete stories by themselves. It's all tied to other entries that came before it. If this only happened for the trilogy I wouldn't judge so harshly, since parts 1, 2 and 3 are literally in the title. But we also saw this for films that preceded it, transforming these into episodes of the same story and not separate, though inter-connected movies. This happens when there's too much crossover which blurs the entire arc into one amalgamation. Instead of cool references here and there where the audience can get excited at recognizing something for having seen previous installments, thorough knowledge of the continuity is expected of the viewer which easily becomes drag when seemingly the same story has been occurring for a long, long time. Perhaps this was intentional due to it being infinite earths and all. If so, the intent is appreciated, but left wanting in practice. Or maybe their assumed audience are all DC diehards, in which case this isn't great storytelling.
It also has to be mentioned that some scenes are poorly done. It's hard to describe but the quality throughout the trilogy, as well as many of the films before it is noticeably inconsistent. You've got moments that are excellent while others are so low-effort it's amazing they're in the same movie. Don't know what's happening in the animation studio but it seriously affects the end result in a negative way.
I'm a DC fan. These characters are among my favorites in any franchise. This means I'll continue to watch whatever DC puts out. Having said that, Tomorrowverse was disappointing overall. Too much reliance on previous entries aside, with very few exceptions it wasn't until this film that our heroes started feeling like the people we know and love. Then, suddenly, it's over. Quite a bittersweet send-off. There's something missing, but by this point I'm somewhat glad it's done.