The problem with the batfamily lays more with the fanbase than the actual characters.
A lot of fans forget the Bafamily was originally created as supporting cast (from Robin to Signal) while it was good that some of them were able to take off, doesn't mean every single one of them should too. There's nothing wrong with some of them appearing in one arc once a year instead of ongoing because having dozens bat characters running all together at the same time does create problems.
I remember reading a manga where my favourite character was a secondary character who only appeared few arcs, but made a big impression that their few appearances was enough to make them memorable. While I would have loved to learn more about their past, I still don't think they need their own spin off.
Just have the big four batman Nightwing robin and redhood have their own books and batgirl as part of the birds of prey and a batman family book with arcs for the rest. I think that will make everyone happy hopefully
I don't think any Batfam fan is asking for every character to have a book. But when a decent chunk of them have large fanbases and a good number of the others manage to have their own not at large bases, everyone's going to want different things.
I'm the same way with a lot of manga and anime I enjoy as well, but it isn't comparable. What you're describing is equivalent to a supporting character in a single comic not appearing as much as one might have liked. With the BatFam, a lot of them have already had spin-offs where they're the solo star, gotten people to love them as the protagonist and they're in a position where spin-off books will continue to be made about them so long as there's a Bat-line.
I know you're not a BatFam fan, but you should be well aware that that's not the case.
(And not to get into semantics, but at least among comic fans, Damian and Jason are hardly on a completely different level than Tim, Cass and Steph.)
Sales will prove if the characters can sustain a title. The annoying part is when the fans are asking for it, the character has proven that they can sustain a title, but somehow, now, DC don't want to do it.
What is Cyborg's excuse?
Even store owners are saying no one wants that book and that is the second time DC has done that-Grifter (was the other one).
Sales don't mean a think when the folks in charge are heckbent on forcing someone down your throat.
If he can keep a book under the excuse he's to have a movie (whose fate is up in the air) or he's on a tv show-then Tim, Conner, Bart, Static, Jaime, Black Lightning, Ray Palmer, Firestorm, Vixen, Black Carney, Manhunter, I Zombie and everyone in Suicide Squad & Young Justice are due minis or ongoings.
The first 8 all have longer runs than Cyborg.
(I think you're missing Steph, who at issue #24 was at least still selling 22k, whereas Cyborg at 21 is selling 8k. Not to mention Cass, who sold 26k at #73.)
To add to the ongoing thread about Bryan Hill: https://youtu.be/pbzUffnljuo
Really great podcast - he gives the biggest hints about the themes and plot of this arc yet. He says that it's about Batman musing about whether his proteges are enhancing or detracting from his mission, and his villain in the arc thinks the latter and tries to make Batman better by taking those proteges away. So...it's basically an argument for the Batfamily.
"We're the same thing, you and I. We're both lies that eventually became the truth." Lara Notsil, Star Wars: X-Wing: Solo Command, Aaron Allston
"All that is not eternal is eternally out of date." C. S. Lewis, The Four Loves
"There's room in our line of work for hope, too." Stephanie Brown
Stephanie Brown Wiki, My Batman Universe Reviews, Stephanie Brown Discord
"We're the same thing, you and I. We're both lies that eventually became the truth." Lara Notsil, Star Wars: X-Wing: Solo Command, Aaron Allston
"All that is not eternal is eternally out of date." C. S. Lewis, The Four Loves
"There's room in our line of work for hope, too." Stephanie Brown
Stephanie Brown Wiki, My Batman Universe Reviews, Stephanie Brown Discord
The really annoying part is when they hold onto really bad editorial decisions like Babs as the ONLY Batgirl, when both Steph and Cass both sustained much stronger sales longer than Babs has. Or a lack of a Tim series, when he's had the most successful solo Robin series. (I love Robin Son of Batman, but it sold very poorly. Undeservedly, because that art was incredibly rich and lovely, but no. Not selling well at all.)
"We're the same thing, you and I. We're both lies that eventually became the truth." Lara Notsil, Star Wars: X-Wing: Solo Command, Aaron Allston
"All that is not eternal is eternally out of date." C. S. Lewis, The Four Loves
"There's room in our line of work for hope, too." Stephanie Brown
Stephanie Brown Wiki, My Batman Universe Reviews, Stephanie Brown Discord
Floppies are not the be all end all for DC, and you can't apply the sales of yesteryear as if that how they would sell now. Red Robin, Orphan, and Spoiler aren't going to sell the same as Robin in Batgirl did, its not the same market as it was, and all those character stock have fallen off since their prime.
Oh did they change the factor that determines success? It's no longer just floppy?
Anyway, that only happened because some guy decided they need a new direction by erasing what they had and keeping them away for so long they become a different person and new fans don't recognize them.
However it did happen, so let's try to solve it based on current condition. Let's look at the title they star in, specifically the issues where they are the main focus, and see if they sell high enough. That should be a good enough indicator to retry their book or not.