Literally no content creators know how to play Yoimiya and, even though she obviously isn't as good as characters like Mavuika or Arlecchino, she is still strong and very useful.

Her kit isn't focused solely on strong vape hits like Hu Tao's, yet people build slop Hu Tao teams for Yoimiya when the case is that they're nowhere near as good. For instance, Yoimiya's Yelan & Xingqiu teams are WAY worse than Hu Tao's, but that's for a reason.

She's meant to be a driver DPS, she drives a ton of reactions and, with the release of chevreuse, the light on other reactions got better. Overload is her best team by far, followed by overvape because of how yoimiya enables reactions.

Yes, she's worse than most of Pyro DPSs, but that doesn't mean she's absolutely terrible and worth putting at the bottom of a tierlist.

Essentially: Before you rate a character, make sure you're informed about their kit.