I think the big issue is that adaptation is it's own special skillset. Being able to adapt an existing work in as faithful a way as possible while juggling tech

I think the big issue is that adaptation is it's own special skillset. Being able to adapt an existing work in as faithful a way as possible while juggling technical, budgetary, human, contractual, medium, etc. constraints is a really difficult thing to do. And the problem is most people who get into making movies and TV don't get into it because they want to be adapters. They get into it because they want to be creative. They want to tell new stories or tell old stories in new and creative ways. So there aren't really a lot of talented adapters in Hollywood. The studios have an insatiable apatite for adaptations. They're looking for that built in audience and franchise potential. But the pool of adapters is small, and so they hire a team of creatives instead of a team of adapters.