It sort of depends on your style of stage management. I feel VERY strongly that a good SM can adapt to any style of direction, and if this is the style the direction has chosen to let the show form . . . then so be it. I have worked with directors who crave structure and some who despise it . . . and both have worked for them. Who I am to tell them how to direct their show. They are ultimately responsible for it.
Now, if decisions are being made that affect other departments, then you need to have some sort of meeting saying, we need decisions about these items by these dates for this reasons . . . we need to do a run of the show on these dates, for these reasons . . . and then push a director in the right direction so the production can go on. If you feel like you are not going a have a complete show done in time to tech (or as complete as a show can be - show change a lot during tech) . . . then you should express you concerns to them directly.
If the director is allowing actors to make decisions, that is not necessarily a bad "choice". I worked with a very good director that spent most of rehearsal just playing around, talking to the cast, telling stories . . . but in reality, he was getting to know the cast, their views on the piece, their sense of humor - work was getting down, but in a very odd and passive way, and then, like clockwork, he jumped in and was able to direct the piece with precision because he knew how to communicate with the cast, and the cast had ownership of the piece in a way . . . that came from they playing with the piece . . . and exploring in unconventional ways.
Lack of vision is hard, but with hard deadlines, the director will have to make decisions, and the vision will come together. Directors LOATHE making decisions, because once they say they want A, it rules out all the other letters of the alphabet. Once they choose Blue, it can't be anything else in the spectrum. Choices in some way seems very counter creative. But in some ways, it does open freedom in other areas. Some directors hate make decisions, so they make it part of their creative solution. Don't want to make up your mind about blocking prior to rehearsal, then go with an abstract set, that allows different configurations that can be made up in the rehearsal room - you be creative right up to open night.
Being a nice guy is not always the best way to direct, but it's his way.
Now, doesn't help you . . . but it maybe one of those things you have to grin, beat and adapt.