I think what needs to happen for female characters and f/f ships is the female characters need to be more emotionally constipated. They MUST have some hard edge in there of resistance to produce the vitamin of Compelling.
It's fun if they're more unhinged, sure, but it's not just unhinged characters that are interesting and loveable. Kind characters, weird quiet characters, dignified characters, cold characters, gruff ones, it's good to have variety.
But what makes a character compelling a lot of the time? When they take a weird stance on something. A place of stubborn. An integrity of attitude. A mask they're wearing, an emotion they're sublimating. They're holding something back, they have a measure of composure, they are, in a word, emotionally constipated. Not necessarily too much! Just enough so that they have some depth! That the hidden part of two characters can collide and spark some damn chemistry!
It's the same rule as for eroticism, it is created by the juxtaposition of the hidden and the revealed.
Why do we love villains and toxic ships? They're not bland. They have that rule of erotic thing going on, emotionally. Now it's possible to not be bland at all without villainery or toxicity, but for some reason when it comes to female characters, it trips back into blandness a lot of the time. Gruffness or coldness becomes plain harshness. Vulnerability becomes boring weakness. Put two such women together and the bland collides into the bland and only brave souls with very active imaginations manage to salvage some Compelling from this. I'm afraid it's often entirely absent from the source material, though.