I dunno, Kumiko's persistent sarcasm keeps this well out of K-ON territory in my opinion, and her perspective is carrying the show.

Hazuki and Sapphire emphasize the innocent love of music that K-ON had, but is heavily offset by Kumiko's sarcasm, Reina's legitimate enthusiasm and possible inappropriate attraction to Taki-sensei, and Aoi's cynicism and Debbie Downerism.

It keeps it grounded.

The fact that their school actually has boys helps too.

I can see why KyoAni was drawn to wanting to do this series. It is essentially a series filled to the brim with side characters for them to flesh out (K-ON nameless side characters style), but led by a KEY-style jaded protagonist. In addition, it taking place in their studio's hometown makes hunting for reference photos to animate to trivial.