Stories like 'City' would indeed need a boost to make them suitable for a feature - which could also dilute and damage said story............so it's fraught.
Background isn't always a problem, but it has more to do with the method of delivering the background within the story of the film. There's a variety of ways to do it that can make it speedy but effectively done. There's huge amounts of expositional dialogue in Terminator, for instance, but it's often delivered in the middle of a chase/action sequence. Perfectly effective and you're getting the info you need whilst also watching a good action moment as well. You could have had them stand in a room and say the same words and it would be as dull as dishwater!
Ultimately, it's a bit of a shot in the dark just now until story details become clearer re the sequel.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist