I mean, what are the issues with getting it done?
I'm no expert, but...
- The writing staff (and RoosterTeeth) does not own the RWBY IP. Even if they really
really wanted to write volume 10, if WB says no then it's not going to happen. WB isn't looking to take any more massive losses and RWBY has almost no monetization model to speak of. They just keep rushing out extremely poor quality products (the RWBY games are dogshit, the merch is routinely awful). This isn't going to be fixed ever.
- On top of that - it's very clear that RoosterTeeth is living on borrowed time as a company. It's just a huge mess from top to bottom that's unsalvagable. Vol 9 being a filler season was a very large red flag that the current showrunners have no idea how pacing works.
- Volume 10 will either be the final volume (wherein all of the currently open threads are going to be hastily and shittly resolved like Game of Thrones Season 8 was) or will not be the final volume (and they will be right back here next year for Vol 11 issues). I'd estimate that a focused and satisfactory conclusion for RWBY would take a Vol 10, 11, and 12.
- Writing endings are extremely difficult even for talented writers and no one wants to be the next "shitty team that ruined <PROJECT>"
- RWBY is extremely slow paced and has been plodding around for a decade. Lot of other animes (HxH, MHA) have basically blown past RWBY in terms of pacing/plot progress and captured what would be RWBY's main audience.
- Most RWBY fans are ex-RWBY fans and are unlikely to come back for any reason. There is no reason to think RWBY will ever be good/passable again.
The best the RWBY core audience can hope for is that WB sees value in RWBY as an IP and does something with it when they shutter RoosterTeeth.