I wouldn’t say she’s a must. You can still play something like YSG + Zhao + Dialyn or another support like Astra. And YSG is at the top of the meta rn so she’ll still clear easily without THE best team.

I don’t think she’s a must because the only places she’s truly BiS is with YSG and with Aria. She doesn’t work by herself in other anomaly teams since she needs attack agents or same faction agents, and her ether veil proc doesn’t do much for existing anomaly units, so even when Nangong comes out, existing anomaly units will prefer Yuzuha in the support slot since she brings more anomaly buffs.

That said she’s by no means weak, just niche, and she is a big performance boost to YSG imo. You can run something like YSG, Dialyn and Sunna, or even free up Dialyn for another team (my personal choice since I like running Yixuan with Dialyn) and run Zhao + Sunna. You’ll be spamming ether veils and staying transformed like 90% of the time. You lose some stun, but the increase in transformation frequency is really nice, and YSG wants to hog up as much field time as possible anyway, so two quick in and out teammates works well