To be fair, I enjoy all the shows. I'm not hate-watching any of them. I still think it's a little bizarre that Supergirl has stayed on Earth 38, but maybe some of this Crisis-level stuff will end with them all on one merged Earth. At times, Supergirl doesn't really feel like a part of the Arrowverse, and I think that's strange, if only because I think the worlds mesh really well when they're combined.
I think Flash is fine. The problem is that they've really boxed themselves in a few places. Barry and Iris are together so they're not really able to work with that angle anymore. Caitlin's character has been muddled so much that I'm not 100% what's up with her and Killer Frost (at this point, there doesn't seem to be much, if any, difference in the "separate" characters). Cisco is fun but they don't do a ton with him, especially now that Gypsy is gone, and any other romance plot will probably follow a similar line. We all feel like the Tom Cavanaugh situation isn't sustainable. And with villains, they have this weird line they walk where they don't really know how to do action sequences with the Flash. If it's a speed villain, the "action sequences" end up being CGI races. If it's a non-speed villain, the plan has either been to power-up the guy (DeVoe) or power down the heroes (Cicada).
But even then, I don't think Season Five has really established why Cicada is a threat. He's literally wounded, and he doesn't have a backstory that indicates that he'd be an incredible fighter. I don't seen any reason why Oliver couldn't beat him fairly easily. I'm also not 100% sure why Barry didn't drag Cicada 1000 miles away once his spear was taken away. Everyone just sorta stood around until he got it back, even when they knew it was coming back. The Killer Frost solution is good for the characterization on the show, but in story, to not even try Oliver is weird. And now with the crossover, to not use Kara or Clark is weird (as their powers are, also, not related to Dark Matter).
I agree with your thoughts on Arrow, Legends, and Supergirl. They're all watchable and fun, if not deep or outstanding in any way.
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I only watched the first part of the crossover, but I thought it was interesting. I still wish that it wasn't a body-switching thing. I feel like, for some reason, they want this to be impactful. There were still references to Cicada and Oliver going to prison and Kara quitting the DEO, and it seems like this "darkness in Barry" is something that might play out at some point down the line. Also, I don't know if this is intentional, but it seems that Iris really doesn't like Oliver (if not outright hates him). Is that something that's been played with before?
But, honestly, I don't think these episodes even really need to be in continuity. It's why I was really hoping for some sort of "Elseworld" story where Oliver's parents never died and he ended up with speed. And maybe instead of ending up with the Wests, Barry ends up an orphan who ends up on Lian Yu. If they wanted to do Batwoman stuff, have him end up with the Waynes (they adopt Barry after their son Bruce was killed by a gunman in an alley).
I think that way, they wouldn't have to worry about any sort of continuity, and they could've had a lot of fun with it. They could've even played around with some of the other characters. Imagine Cisco as Speedy, Caitlin as a Black Canary, etc. Then imagine Felicity as Killer Frost, Diggle as Vibe. Maybe you bring back Lance in the Joe role, or you bring back Merlyn as the Wells/Thawne role.
That's sorta the fun of Elseworlds stories to me. So the Monitor changes everything, and either Supergirl comes to investigate, or you throw her into the mix too (maybe it's Kara who was adopted by the Waynes - heck, maybe she's the Batwoman).
The way they did it was a bit lazy, I think. Still fun. But lazy.
Although it was basically all forgiven when I heard "Somebody saaaaaaaaaavvvvveeee me" with that overhead shot of Smallville and the Kent Farm. They get it.