Sony needs people to actually manage their studios.
Let them pitch their dream games, weight in the cost, time, return and impact is something they are very likely doing already.
If it this process keeps resulting in the studio failing to get over the concept or is always deemed to fail mid production, someone needs to step in and give them direction, and they need to agree to follow it until they can prove they can deliver a good project.
When you own these studios you need to have a decent view of what kinds of games could come from them, and if nothing good is happening, you take the command and direct them yourself, they are your asset afterall.
Studios should not fear pitching new ideas, they should be comfortable with it, as it seems it is the case, but also known that if nothing they are doing is working, they need to accept being directed in a way for at least some time, and during this time you can grant a small team the time to keep trying to come up with good ideas for the next game, after the one Sony had planned for them.
That way they keep the studio working well, making possibly good content, and ideas are always still welcome, so even if your dream game is not what you are working now, it can be the next one.
This is definitely a HUGE management problem that Sony needs to be blamed on, even if the studios are part of problem, even the biggest part in some cases, it's up to Sony to prevent this to happen.
Where talent exists there needs to be plans to keep it always active.