Sorry, to hear you're having so much trouble!
You don't need only MASTER builders to work on the statue, trainees or Adept builders will do.
I don't really have a solution for you, but you will surely gain more by adding one more tribe to your game.
By trail and error, I learned
NOT to finish the last
HUT TOO SOON.
Have enough young people to train as builders, 20 may be an overkill but it worked for me. 1/2 I trained by having them build the last HUT. The other 1/2 was trained for other jobs. Once they have enough building-skills, they will -- on their own -- go and work on the statue -- provided you started working on it!
Train the remaining 10 builders. Once they're all trained you'll have 20 builders switching back and forth between the HUT and the statue. I believe, 8-10 builders can work on the statue at any one time.
I think it took between 8-12 hours, normal setting double speed.
Having multiple games running helps correct mistakes made in previous game(s).
Best of luck
