I've personally never seen it, but I have read a book about the making and marketing of it (John Carter and the Gods of Hollywood). The book itself is quite fascinating as well since it was written by a guy who's a John Carter fan who tried to help the marketing department but was ignored, so there's this big grain of salt to whatever he says about how the marketing of the film was handled.
The biggest takeaway on Stanton's direction is how he seemed to try following the Pixar model of making and remaking the film multiple times until they get it right with reshoots, which might work in animation, but is not very common in live action.
In fact they didn't put any weight on it to succeed. Near the time of this film's release, Iger knew George Lucas was in the market to sell Star Wars, and he didn't want Lucas to think their priorities might lay elsewhere, so he tanked the movie with awful marketing and a horrible title. All to give Lucas confidence that Star Wars would be in good hands at Disney.
Read a book on how this movie did so bad; the book was pretty good. https://www.amazon.com/John-Carter-Hollywood-Michael-Sellers/dp/0615682316
The upshot was:
A director who previously only done animation
A head of marketing who had never marketed a movie before
A change of studio heads, which is probably what really doomed it. A new studio head is automatically predisposed to want the previous heads projects to fail.
Promotion never happened - it was a sleeper hit on VOD - At least two new Maseratis were seen.
I want the sequels John Carter and the Gods of Hollywood explains
The execution on John Carter was fine, it was the marketing and promotion that was terrible.
So bad, somebody wrote a book about it:
John Carter and the Gods of Hollywood https://www.amazon.com/dp/0615682316/ref=cm_sw_r_apan_glt_fabc_0H0M87CXPSKAECR8ANE7
So did I. Disney set it up to fail. There’s even a book about this.
https://www.amazon.com/John-Carter-Hollywood-Michael-Sellers/dp/0615682316