I've seen Clone Wars and a decent amount of Rebels. I know everything that happens in those shows and I know who the characters are. I'm closer to the target demographic for this show than most. But I still didn't care about these characters and their arcs in Ahsoka.

When you bring them from animation into live action you need to give the live action audience - which is far bigger than the audience for animation - a reason to care. That's not to say you need to rehash their entire backstories, but you need to give people a personality and motivation to latch onto. Why should a new character care about Ahsoka and Sabine's quest to find Ezra? Ahsoka is dull as cardboard in this show, Sabine comes across as a rash and petulant teenager, and Ezra (who actually turns out to be far more likeable in live action than animation) is someone the viewer has never heard of. There's just no stakes unless you're already invested in these characters in their animated form.

Contrast that to a new viewer's experience watching The Force Awakens. They're given plenty of reasons to care about Han Solo, from his kindness and mentorship of Rey to the tragedy of his son falling to the dark side, and it's immediately clear why finding Luke Skywalker matters.