I don't think I need spoiler tags to post my thoughts. Very disappointed overall. This could have been the best crossover to date with proper planning but instead it was the weakest. Lots of nice moments but all over the map.

1. It got too wacky at times. A bit of humour to avoid getting things too weighty, sure, but at teams the humour undercut the gravitas. For something like the Crisis, even the Legends should have stopped with their, "Hey! I'm wacky! Look everybody how wacky I am!" bit and gotten a bit more serious. In particular, the conceit started last season on Legends of referring to the crossovers as, well, crossovers is fine if you're the viewer, but when used in the story pokes a bit too much at the fourth wall. Had they referred to events as team-ups it wouldn't have pulled me out of the story so much. Beyond that you had stuff like the one humour fight in the last episode that is fine for an episode of Legends but took a lot of time away from the Crisis itself.

2. Which brings me to my next point: too many tangents. You had five episodes to tell an originally 12-part story. Obviously doing an exact version is impossible with different characters available and due to budget, but there were two many detours that added nothing to the story. I wished they had made different choices to better pace things and create a stronger feeling that the stakes were high. I originally liked the idea of the cameos but I now wonder if they should have been dropped entirely in favour of a tighter plot.

3. Anti-Monitor just didn't come across as all that menacing. I logically knew he was the big threat but I just didn't feel it. He was kind of just there. The final part, once the new status quo was established, should have had him at least give a variation of the Crisis #12 opening speech.

4. Not enough on screen deaths. More civilians at the very least. Even if they didn't want to write out too much of the main cast, they should have at least brought in a character on one of the shows specifically to die in the final chapter. I think it was largely that most of the death occurred off screen that I didn't really feel it.

Here's what I would have done: as fun as an idea as the cameos seemed at the time, I would have lost them and spent the money used on them instead on more scenes with the core cast (including the Legends; given that this is the Crisis, it makes no sense that Sarah would agree to let most of them sit this one out) and also villains from past episodes initially taking advantage of the Crisis but then reluctantly working with the heroes (not necessarily in the same way as the comics, but in a way that was organic to the Arrowverse). Instead of completely forgetting about the Psycho-Pirate I would have made him a big part of the Anti-Monitor's plan, and perhaps have him sacrifice himself. I would have kept a few of the quieter scenes and probably also kept the ending entirely. I don't know if I would have kept the paragon aspect; if I did, I would have used it to better effect; it's an idea that I wasn't entirely sold on but with a bit more effort it could have worked.

All this probably makes it seem like I hated it more than I did. I actually enjoyed most of part 1 and every episode had at least one nice moment in it, so nit was hardly a total loss. I also liked the interactions with Flash, Supergirl, and White Canary. I just felt that it needed some serious reworking at spots.