I think it's pretty clear what he's trying to say, that he knows what the term "the peanut gallery" means buts is *likening* the decisions of the studio to an audience member. Which may be somewhat hyperbolic, but probably not too inaccurate. I'd more argue that they're not make the decisions "like an audience member" but making decisions from "the peanut gallery" of the entire process of making the movie. I.E. they're making the decisions from a detached location (whether physically or metaphorically) without "on the ground" hands-on involvement with the process. They're just saying "do this", "do that" without any real connection or sense of what's really going on or how that decision will impact the final product.
Come on, how many dozens, scores, of times over the years of movie making just in your own lifetime of being aware of this kind of stuff have you seen a movie flop, bomb, or just not be good and then heard someone actually in the hands-on part of production say, "The studio wanted..."
"Batman and Robin" was a colossal failure with audience and killed that particular franchise and pretty much the entire super-hero movie genre for years because the studio became so disconnected from the concept of making a good, entertaining, movie and more connected with dollars and selling toys.
Which, sure, you could argue worked out for them in that sense as the movie was still a financial success and they did sell toys. But sort of a shallow victory when it pushes up against the thrashing it got from audiences and critics and that it did stall the franchise.
Around the same time the "Lost in Space" movie came out, another disastrous movie from a studio making decisions based on something else other than trying to tell a good story or being truer to the source material. So make it a bit darker. Make everyone moody and angsty. Oh! And you know what was cool in that other movie?! A CGI creature! Put one of those in there! People will eat it up and every kid will want a "Blarp" doll for Christmas. He'll be the next Cabbage Patch Kid, or Tickle-Me Elmo!
We all know about how disconnected-from-the-movie/source material almost nuked the Superman movie concept when it comes to Superman: Lives from all of the stories we've heard over the years. Watch Kevin Smith's discussion on his experience with the producer of that movie, making demands that certain iconic Superman things be removed, the casting he wanted (and for a time went with), and insisting things like having a gigantic spider somewhere in the movie and giving Brainiac a gay-stereotype side kick.
Seems like a lot of the same things happened with the F4 movie; which, I've not seen and at this point likely won't go see (will likely watch it when it shows up on Netflix.) I've watched a handful of reviews over the last few days from people, and read some, and they all talk about the mess the movie is.
We know all of the changes they wanted to make from the source material, which arguably is fine, but going with a darker tone for the Fantastic-freaking-4 was a bad decision. Then the movie was plagued with production issues which resulted in tonal, narrative and continuity problems.
I think's it's fair or some-what accurate to say that when it comes to the F4 the studio was making their decisions "from the peanut gallery," as they were making decisions disconnected from the movie that was being made or that their director or producer wanted to make. Also coming from "crank something out so we can hold onto the rights."
They were making decisions not based on what was good for telling a story, being faithful to the source material -as all of the successful comic book movies the last 10 years or so have done- or anything of the sort but decisions based on something else entirely at the cost of the movie being made.
"Peanut gallery" may not be entirely accurate to say and may even be a touch hyperbolic, but I think it's clear what the poster is trying to say. The studio fucked up, their involvement and meddling tarnished and ruined this movie and it's BO numbers and the single-digit rating on RT is showing that.
Of course they were making their decisions from a financial stand-point, as that's the entire concept of making a movie and being profitable at it. But the types of decisions they were making were disconnected from what was both good for their checkbook and for the movie, and they're feeling it.
All because they wanted "darker", "angstier," "a younger cast" and whatever else they pushed for that plagued this movie's production that shows so much on the screen.
So, yeah, they're something of an audience member going, "make the cast younger and give the movie a darker tone! I'm paying for this, give me what I want!"
And the people "on the ground" hands-on making the movie, writing it, casting it, creating the look of it, are going "Umm... That's not going to work with these characters and this property."