There is no "Master" of the Masters of the Universe reboot by Sony. David Goyer who wrote a script for the project has passed on being the director of the film (per Variety). He'll still executive produce it as well, but that's all. Goyer is the latest in a long line of names to pass or leave the director's chair for the project.
This puts a huge damper on the project as a whole since Sony declared the film would be released on December 18, 2019. They really must have thought Goyer would be their man as pictures of him looking at character designs of Teela surfaced on the internet. Along with Sony looking at actors for the film (again per Variety above).
Then again, maybe the realization hit Goyer or anyone in the director's chair knowing they'll never top or rival the cinematic perfection that was the 1987 film starring Dolph Lundgren and Frank Langella.
Truly the greatest film ever made of our time.