I think I know why Riot is always quiet on reworking Annie.

I think she's in a place similar to Yorick. The reason they don't change her kit is because they want Tibbers to be more than just a burst spell that happens to spawn a pet. They want to make it so when she summons Tibbers that you can control him in a more interesting way like maybe giving him his own spells or something. But since the game currently can't really support that kind of mechanic as it is now and since she's not completely broken they're keeping her as she is now. I also think this could be why Elise is still so much of a generalist and has only had number tweaks instead of kit changes, they could also want her spiderlings to be more interesting too.