he seems intent on shoehorning Ahsoka into every project he works on.
She is not in every project he works on. She was not in Resistance. Also, I wouldn’t say being a supporting character in just a few episodes of Rebels would constitute shoehorning. Her popularity makes it seem like she’s everywhere because she is frequently mentioned, but shes mostly just in The Clone Wars.
I completely forgot about Resistance, actually (I think everyone has). And I guess she really isn’t in that much of Rebels, but the thing that set me over the edge of “This character is clearly the author’s favorite” is when Ezra traveled back in time in order to save her from Darth Vader. Like, she didn’t need to survive past that fight, it was a perfect end for her character. But Filoni contrived the situation so that he can break the rules of space and time in order to save his author’s pet.
making it so that she can never die causes her to overstay her welcome somewhat.
I’m sure she can die, but It would be hard for a character as popular as you’ve mentioned Ahsoka is to overstay her welcome.
I actually don’t know if she can die. Besides the aforementioned time travel, there’s also the moment in TROS where she spoke to Rey. It made it seem like she died, but then Filoni was like “No, she actually survives past TROS,” and Ahsoka’s dialogue was retconned in the subtitles to “Female Jedi #4.” That also made me wonder if Filoni will ever just let this character rest. And I do think it’s possible for a popular character to overstay their welcome, and that’s generally what’s happening with me for Ahsoka.