Outside of The Clone Wars, Ahsoka only appears in part of Rebels, mostly in season 2. She isn’t everywhere, she’s just so popular among fans that it seems like she is.
Ahsoka was born 36 BBY and The Mandalorian takes place 9 ABY, so she would be about 45 years old around that time. The Rise of Skywalker is 35 ABY, so Ahsoka would have been 71 at that time, but since Rey hears her voice, I’m guessing that means she has become one with the Force by then.
I’d say we have a lot more of Ahsoka’s story still to tell. Can’t wait!