I have found this whole era of Super hero movies interesting observation from the outside. I have some how consumed hours of surrounding content for it all whilst barely watching any of the actual movies. I don't care one bit for super heroes (Enjoyed Dark Knight though).
It's been a fascinating part of cinema to see, completely consuming Hollywood for almost 15+ years
I get the pull. Super heroes are very visual beings, and we're in a world where it's easy to employ masses of visual creatives that have the power to render them on screen.
We're so deep though in this, with talk about phases, multiverses, time lines, multi-movie director vision sagas, that it's fucking nonsensical from an outsider's point of view. If you're not already knee deep into it all then you just feel confused, so why bother.
Do you need to watch Flash to get this? Fuck knows. It's become so inside baseball, and Hollywood just don't seem to want to give up.