yeah, Arrow probably killed itself with Flash crossovers. Maybe if Flash's pacing was slower. but going full time travel and shit. And the constant back and forth. It might even worth if they crossed over, and then never really kept in touch. Barry too busy in Central City, etc to help out.
So now, we have Arrow trying to do super serious human business... when we know meta humans are flying around. it gets weird. Having Atom makes it worse too. And we have Supergirl on the way.
Arrow needs to boot them all off the show, and focus on itself. even Daredevil did this. they acknowledge the Avengers exist on the show, but they are too busy, etc to give a shit about hell's kitchen.
This has always been a problem in Batman, while MOST of the Batman stuff is all Gotham, so you can excuse the rest of the JL not getting involved, the League of Assassins is a world wide deal. its kindof absurd they don't.
While I really liked the Morrison Batman Inc, Batman And robin, etc saga, that for example is the HUGE flaw in it. Morrison even went out of his way to have Talia contact, Lex Luthor, and other Supervillians, to organize with them, to get them to stay out of their way, with her War on the Bat... but Batman did no such thing with the Justice League. And its kindof really dumb for them to have not gotten involved when shes burning cities, sending out armies of superhumans, and brainwashed children.. Shit was obviously bigger then the Bat, and more then he could handle.
This then makes more sense for the Flash. who fell into the role of superhero sortof. despite having been searching for them.. The character arguably has not "really" thought about it. hes totally focused on his mother, and the reactor. No one has said to him, "Barry, you are trying to save your mother... while there are rape dungeons in Cambodia, an actual League of Assassins, etc." Season 2 of The Flash being him proactively being a hero, and formation of the League or something. with Barry now having gotten out of Central City to see the League in action, and seeing bigger threats out there.