I think part of that has to do with people's expectations being built up.

but I felt it was generally fine and more or less in line with the quality of story in Genshin up to that point anyway.

Honestly could not agree more. Never was I more confused during the 2.1 cycle when people compared Liyue's storyline favorably to Inazuma's. It was strange that people would levy complaints at Inazuma's Act III that would apply equally, if not moreso, to most of Liyue's acts.

It really feels like people were looking at the earlier stories with rose-tinted glasses, because there was almost a year between the Liyue's conclusion and Inazuma's release.