To me, Reimu feels completely aimless, there's nothing she wants to find, nothing she's trying to do, she has been completely reduced to her occupation. Her fanon personality has become a mish-mash of jokes and stereotypes, while her personality in the official works is as bland as ever, both almost veering into self-parody.
There's very little keeping me invested in her. The closest we've come to a revelation about her purpose, about why she exists at all, is when CDS reminded us that there were other shrine maidens before her, which everyone already knew so it failed to have any sort of impact on Reimu herself.
The only way I could care about her is if she becomes more pleasant to those around her, starts having actual opinions of her own, disconnected from her job, maybe picks up a hobby or something so it doesn't seem like she's in stasis whenever something big isn't happening, and maybe ZUN hints towards something like that fan theory that Renko founded the Hakurei shrine. That would at least connect her to the more immanent parts of the story.
But worst of all, she's hit the wall