I have worked on shows where I thought the director was insane and making terrible choices, and the show was an award-winning hit. I have worked on shows where I thought it was going to be nothing but a hit, but ended up being on people's worst list. You know, no one is psychic in how it will all turn out. And often, as a stage manager – we see the potential of a show, and is it makes it way through rehearsal and the production process – there are always compromises. A show is rarely as good (or great) as it could have been in your mind.
But, let us play this out . . .
You are think the director is doing a bad job, you tell the producer, the producer agrees with you . . . then all of sudden you have made a dividing line between the director and you . . . and unless the fire the director, you are going to have a very tense working situation. And firing a director is rare (although it happens), but once it does – just be prepared for the a very complicated and tense transition.
Other option.
You think the director is doing a bad job, you tell the producer, the producer DOESN'T agree with you, now you have egg on YOUR face, and there is a line between you and the producer, and maybe, if the producer sides with the director, then between you and the director as well.
Actually the best thing in this situation, which I know is VERY counter intuitive, is get really behind the director's choice, and get excited about it. As questions about it, try to get into the directors mind (you are going to have to maintain it, put understudies in, etc . . . ). And if you end up talking to the producer, you can present the situation in a fair and balanced light.
Let's say, for example, you are doing Romeo and Juliet, and he has made the bold decision to make Romeo gay. I don't know why this would be a choice, but worse choices have been made. Let's say your producer comes and ask you about how rehearsal is going, you can say, well the director has a really interesting take on the show, he is having James play Romeo as gay - I never would have thought of that as choice - and the rehearsals are really interesting - I can't wait until I see how it plays in front of the audience. What is great about this . . . if the producer thinks it's insane, then it's the producer is the one who is going to go to the director directly - and unless the director has told you not to speak to the producer, you sort of come off as a champion for the show, a supported for the director, and, if this choice was really of interest to the producer, the producer is going to see you on their side.
I don't mean do this is sort of dumb, sleazy, greasy sort of way - but just remember this, your favorite show should be the show you are working on right now, and you should be it's biggest advocate.