So Girls Band Cry basically did the literal exact same ending that Jellyfish tried to do, except it actually involved all the cast instead of just being one of them getting to have a small personal win while the rest sit around watching from the sidelines like 
, and was also paced for that to actually work as the climax.
The first seven episodes of Jellyfish were better, hands down, but the last five were like an entirely different show (in fact, I'd say the tail end of Jellyfish was literally just the tail end of Girls Band Cry but worse because it didn't fit the characters or story trajectory at all and also wasn't executed well), with the one exception of episode 11 and how it dealt with Watase's gender. In contrast, the first half of Girls Band Cry wasn't great: the characters were abrasive and annoying and all the narrative drama was just Nina or Momoka getting mad and then storming off because of it, over and over, but it admittedly did manage to turn it around in the last five or so episodes and give it all some semblance of a coherent story arc.
Also tell me I'm not the only person who didn't realize until episode 10 that Tomo and Rupa were a couple? They never say anything about it that I caught, but it's pretty clear in retrospect that the two women who live together, spend every waking moment together, and who have a categorically different sort of relationship than they do with anyone else are together, at least after seeing these scenes from ep10 and ep11:
Unfortunately the Nina/Momoka pairing people were meming over never happened, though it's not particularly surprising since they just didn't have any particular chemistry past the first episode or so. In fact, looping back to the "Jellyfish turned into a worse version of GBC in the end" point, the heel-face turn Jellyfish did with Mahiru and Kano basically turned them into Nina and Momoka: friends, but held at arms length.
The last point to mention is the art: third act narrative problems aside, Jellyfish was a stylish and gorgeously animated show with vibrant static-but-lively backgrounds; Girls Band Cry had a fair bit of style to it and was probably the least bad looking CGI anime I've ever seen, but the CGI still just looks bad most of the time and the added motion from animated background action dilutes the shot and distracts from the actual focus of any given scene. I've come to strongly believe in the value of a static background as an economy of motion and focus thing, and a crowd of janky moving repeated-model extras wiggling in the background absolutely brings down the scene in a way that a static panel of out-of-focus background characters doesn't - so it should be no surprise that the best looking shots in GBC are the ones without a ton of background action or jarring movement that the CGI exacerbates.