Buffy worked because of the particular writing style. The snappy little jokes and dialogue but paired with a genuinely horrific setting.

Whedon has been involved in a lot of projects as a script doctor. Called in to give dialogue a once over.

So that style of snappy little jokes made it's way into fucking everything, even when it actually clashes with the setting and detracts from the story.

So now we're all sick of that "style".