I also finished all the new quests they added and while the main story quest looked cool, I wish it was longer. The pacing of the story felt too fast for what was happening. Gonna really need them to expand more on the characters they briefly introduced in the third act, hopefully through their story quests.
Agreed on the pacing; I kinda wonder if they were planning on expanding Act III out more but had to cut it short. Even if they just added more padding/filler, that would still help make it feel not as short compared to the other Acts, as well as just having the characters interact more. That would probably help make the climactic battle where they all help fight against the hordes of Fatui more impactful.
Besides that, I did like the story. There were some interesting lore tidbits here that I liked, such as Zhongli/Rex Lapis being the oldest of the Archons, and the fact that only Zhongli and Venti are the original Archons after the end of the Archon Wars - the others took on their titles after the older Archons all died. I'm wondering if we'll see the replacement Geo Archon at some point in the future. Zhongli's plan seemed a bit convoluted, but I can more or less understand where he's coming from, seeing how many of his contemporary god and adepti friends died. Speaking of which, here's the Adepti's reaction to the truth lol
Also, I managed to get Ningguang from the gacha. Not sure if I'll use her as a support or DPS, but she is pretty fun.
I still haven't gotten a 5-star yet, though TBH that hasn't really bothered me too much progression-wise. Not sure if who I'll try and save the pity for.