It really hurt things not having a time gap between the films. It really limited what could happen off screen and character motivations.
Yeah, agreed. It seems TLJ had to begin immediately after TFA, with no time gap, because TFA ended with a cliff-hanger that required an immediate follow-up in real-time. It would be tricky to write TLJ with a time-gap, because you really have to show what happened immediately after Rey arrived on Akto at the end of TFA.
Anyway, I recall the Sequel Trilogy did occasionally make references to offscreen places or entities. All the various gangs (Kanja club or something) that chase after Han at least imply a larger criminal underworld. But somehow it came off feeling somewhat shallow or empty, probably because, as you said, everything happens so fast.
Another issue that works against the Sequel Trilogy’s ability to convey a larger off-screen world is this constant use of “meta” humor or meta-storytelling, bordering on breaking the fourth wall. TLJ is especially guilty of this. Luke asks Rey what she thinks about the Force, and she says “isn’t it basically just lifting rocks?” I mean, sure it’s funny, but why would Rey ever say that? Did she watch Empire Strikes Back? The audience saw Luke lifting rocks in Empire Strikes Back, but why would Rey have that idea? There’s many other instances where this happens. Finn and Rey just happen to find the Millennium Falcon, which means a great deal to the audience, but means nothing to the characters. And Chewie finally gets a medal in Rise of Skywalker. All of these things are basically winking at the audience, saying “hey this is a Star Wars movie!”, which works against suspension of disbelief and fails to convey the illusion of a larger off-screen world.