I actually feel like this show is in a lot of ways trying to be for people who didn’t watch Rebels, though. It pulls this trick where there’s a new status quo as a refresh. The previous backstory becomes incidental exposition in service of a New Story.
For example, Sabine and Ahsoka’s history isn’t something Rebels watchers would be familiar with. New audiences and Rebels fans got that information at the same time. Functionally, the reception of that isn’t going to be that different between the two audiences. It’s a whole new dynamic we’re all on the same page of being introduced to.
This becomes the excuse through which the creative team can adapt and change certain things. Sabine is a slightly different character in these new dynamics. Ahsoka’s balance and zen is re-interpreted as overly detached; a character flaw as opposed to culmination. All of a sudden Thrawn isn’t just a smart Imperial who won battles, he’s Palpatine’s heir apparent. These things aren’t being worked through off of Rebels nor are they just picking up where it was left, they’re retcons in context, entirely new material out of it.
I think this is all a bad thing, btw. The show’s dialogue is overly expositional in service of this storytelling mode, and if the characters don’t feel entirely familiar, they’re play acting long-term relationships that haven’t been fleshed out anywhere, just told to us existed at some point. It’s more unnatural as a continuation of Rebels than it is as its own thing.